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SLP High Flow Catalytic Converter Kit (96-10 All)

Item 23034
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      Review & Installation Video

      Hey, guys. Stephanie with, here with the review of the SLP High-Flow Catalytic Converter Kit, from 1996 to 2010 Mustangs. In this video, we're gonna talk about the materials and construction of these cats, and the install as well. I'll talk more about the install shortly, but I can tell you right now, that I'm gonna call this a two out of three wrenches in the difficulty meter because you will need to make modifications to get these installed. You should check out the SLP High-Flow Cats if you're looking for a two-and-a-half inch stainless steel Cat for a naturally aspirated setup because you're trying to abide by emissions laws. But you still wanna ditch the very restrictive factory cats, for something that's gonna open up volume, and a little bit more power from the exhaust.These high flow cats offer a good compromise between staying legal, and still having a great sounding Mustang. You also might wanna check these out if you have an off-road setup on your car currently, but you're looking to tone down the volume or the rasp a little bit. This SLP kit has two Universal, two-and-a-half inch cats that are stainless steel, with an internal ceramic substrate material. This makes these cats perfect for naturally aspirated builds. If you don't have a naturally aspirated setup, I would recommend checking out some of the other options since there is a set of cats with a metallic substrate material, for the force induction carbs.SLP claims that these will pass most emissions tests, but what I would say is that I never promise all high flow cats pass all state emissions tests. That's honestly just the name of the game, and I can't really guarantee something like that, unfortunately. I will say, though, that if you don't feel like swapping out your exhaust when you have your emissions and inspection, then there's no reason not to try these. When it comes to price, you can expect to pay just under $200 for this kit. It's the least expensive option on the site, although the pipes offered for NA cars is only about $25 more. When you're shopping for cats for force induction carbs, the things get a little bit more expensive, because you need a different material inside of the cat to handle a higher exhaust temp for those builds. When it comes to the install, depending on how you install these, you can expect to spend a few hours, and it's gonna be a two out of three wrenches in the difficulty meter because you will need to make some modifications in order to get these installed. What exactly you need to modify will change depending on if you're cutting out old cats and replacing them with these, or if you're adding these to an off-road system. But either way, it's not a terribly difficult install. You're gonna need a good socket set. Something to cut the exhaust with like a Sawzall with a fresh blade, and a jack and jack stands or a lift to get the car in the air. If you're replacing cats with these, you'll already have your location marked for you, and you can proceed. If you're putting these into an off-road system, you need to mark and cut the mid-pipe to make room for the cats. I would then file the pipe down to make it smooth after cutting. The cats do have a specific inlet and outlet side, so you wanna make sure that you have the orientation correct before installing. And you can clamp these into place or weld them in. It's up to you. Wrapping things up here with the SLP High-Flow Catalytic Converter Kit, this is a kit that offers two Universal, two-and-a-half inches stainless steel High-Flow cats, for naturally aspirated applications. These are gonna help you keep your Mustang loud, or help you tone down an off-road setup, and you can check them out more online right here, at

      Product Information

      Features, Description, Reviews, Q&A, Specs & Installation


      • Improved Exhaust Flow
      • Universal 2.5" OD and ID Design
      • Stainless Steel Construction
      • Ceramic Substrate Material
      • Will Pass Most Emissions Tests
      • Durable Construction
      • Sold as a Set of Two


      High Flow. Are you looking to free up your restrictive exhaust, but are required to use Catalytic Converters? AmericanMuscle has the answer in the form of SLP's High Flow Ceramic Catalytic Converter Kit.

      Durable Construction. These SLP Catalytic Converters are made out of Stainless Steel and a durable Ceramic substrate material making them perfect for naturally aspirated applications.

      Will pass most emission tests. SLP's High Flow Ceramic Catalytic Converters will pass most states emissions testing procedures. However, check your local and state ordinances for installation and usage regulations.

      This SLP High Flow Catalytic Converter Kit is designed for use with Mustangs from 1996-2010 and is sold as a set of two.

      Fitment: 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Details

      MPN# M31040

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (65)

      Write a Review

      Ratings Summary

      4.4 out of 5 overall rating from 65 customers

      Installation Time: Full Day

      Installation Cost: $100-$250

      • January 28, 2020

        5 2007 V6 - Pjw Installation Time: Afternoon

        Great product

        This item increased my throttle response and sounds great.

        Helpful (0)
      • November 29, 2019

        5 1996 GT - JamesD Installation Time: Afternoon

        Great product

        I installed these with cat back Flow Master exhaust. Sounds great. More horsepower than the stock cats. Sounds great.

        Helpful (0)
      • September 02, 2019

        5 2005 V6 - Ro05 Installation Time: Afternoon

        I like them

        The old catalytic converters came apart inside, shut down the engine. Ford wanted $1431.00 plus labor to replace. The parts been on back order with no projected date to arrive. I went with these as I could have them in two days. Glad it all worked out this way, saved a good buck and car runs and idles smoother than ever. I only gave a 3 star on performance as I can't feel any power change, but my fuel mileage did go from 21.7 to 22.4 mpg.

        Helpful (3)
      • May 15, 2019

        3 2007 GT - Alexander Installation Time: Shop Install Installation Cost: $250-$500

        Know your setup and buy accordingly

        Hello on my 07 mustang GT i have a JBA long tube headers with a cat back exhaust(H-Pipe). Just recently my CAT's were starting to make noise so i replaced them with SLP High Flow Catalytic Converter Kit from ( when i first met with the mechanic he said it would require more money due to the highflow cats being larger then the CAT's i had on, he had concerns for it rattling with the heat shield or just causing excess vibrations anyways. He still said he could make it work though for of course just a little more money. i didn't notice the noise until i was down the road and until i got off the highway. If you do decide to get highflow cats i highly suggest you get the Highflow cats from the creators of your existing exhaust set up to mitigate any possibility of a misfit. Besides that, they look really aggressive if you're looking under your car. ***PERFORMANCE GAIN*** The clarity of the exhaust is much better but that's just due to new catalytic converters being installed, the sound i think is a little louder but that might just be a Placebo Effect, I would buy this again if it fit my car properly.

        Helpful (2)
      • February 05, 2019

        3 2004 GT - BryanH Installation Time: Less than 1 Hour

        Not bad.

        Overall I suppose it's my fault! However when I purchased these I checked them both individually, MAKE SURE YOU LOOK AT THEM SIDE BY SIDE! The products I received were completely different and unfortunately I didn't find this out till one was already welded into my car. They do their job however, mechanically speaking I've had no issues with them even though I have 2 separate cats in my car I can't tell if there is any power loss or gain but it did make my car much much quieter! They both fit in rather well (needed some modification to prior pipes) as one was a 2.5in diameter and the other was a 3.5in. But otherwise they work as needed!

        Helpful (1)
      • January 18, 2019

        3 1998 GT - GuyC


        If you have a bbk exhaust system as I do they will not fit and I missed the fact that the exhaust is stainless steel another problem. Wish I could say something more positive the floor plan clearance won't allow them.

        Helpful (3)
      • November 24, 2018

        5 2001 GT - BryanE Installation Time: Shop Install

        Hi flow cats

        These work great. I had them welded on instead of clamps. No CEL and passes emissions.

        Helpful (7)
      • October 14, 2018

        5 1998 GT - Jay53 Installation Time: Less than 1 Hour

        Great cats

        At first I didn’t like them. Thought they were too quiet (had straight pipes before) However, the sound grew on me. Another few things I like. Got my back pressure back so I have noticeable torque gains on the low, now it’s not ridiculously loud so I can actually race around with these and not worry about getting pulled over every ten minutes, and it has a more muscle sound to it now. Cons are now it’s the lowest point on the car. If I’m not careful I will scrape these on speed bumps.

        Helpful (7)
      • October 06, 2018

        1 2002 GT - Maxiandy562 Installation Time: Afternoon

        Not Good

        Lets start off by saying I love SLP products, but these catalytic converter are trash. I got these on 09/12/18, and installed them on 09/17/18. It is now 10/06/18 and heard a rattling noise. lifted up the car thinking something came loose. Nope the rattle was coming from inside the converters. Not sure what to do now, Im hoping American muscle can help me out with a return.

        Helpful (8)
      • August 11, 2018

        5 2003 Mach 1 - DonaldL Installation Time: Afternoon

        SLP purchase and instal

        had to replace cats on my late son's 2003 Mach 1 . he raced it and ran fuel very rich which took out the cats. Bought a set of Magna Flows which did not fit. Very reluctant to order another set online however lucked in to a very helpful parts person and finally found the same units that where on the car. perfect fit and easy installation.

        Helpful (5)

      Questions & Answers (48 answers)

      5 Top Rated Questions

      I have a stock exhaust setup except some magnaflow axle backs will these cats need a tune for them to run or will these be good without a tune?

      • The SLP High Flow Catalytic Converter Kit will not require a tune, however stock mid pipes will require in depth modifications to fit these cats.

      Helpful (5)

      Will these cats add alot of volume to my exaust? I currently have a straight pipe from the cats back along with a small resonator and I'm looking for a little bit more volume

      • Yes, these cats would be louder than your factory cats.

      Helpful (2)

      I have a 2009 4.0 mustang and am currently looking at exhausts, I am pretty set on purchasing the types true dual exhaust x pipe kit, would these fit with that kit or no ?

      • The SLP High Flow Catalytic Converter Kit, as well as any of the high flow cats we happen to offer separately, are made for a universal fit, so it would be unlikely that it would end up being a direct bolt on. It would be safe to assume some sort of modification will be required.

      Helpful (2)

      Do i need to buy mil eliminators with these or will they not set off the engine light at all?

      • High flow catalytic converters should not set off the check engine light.

      Helpful (2)

      Does it need to be welded or is that just preference?

      • These would be a clamp on design and would not need to be welded.

      Helpful (1)
      10 More Questions
      Following my last question, can I just cut my old cats out and weld these in place or will I have to get different size pipe ? Or should it just go in with a bit of welding ? 1 answer
      Hello, I was just wondering if these catalytic coverters will be a direct fit for my 2006 Ford Mustang V6. Also, I wanted to know if they’re California smog legal. Please advise. If they’re not, please advise me on which ones are. Im in need of two. Thank you. 1 answer
      Why do pypes high flow cats require a tune but these don’t? And will these be equivalent to the loudness of the pypes? 0 answer
      Hello, will these throw on a check engine light? 1 answer
      Will these be a lot louder over stock cats? And if doesn’t show any codes can I get away with not tuning it after installation? 0 answer
      Do these pass smog in California 0 answer
      Do these have O2 sensor bungs? 1 answer
      How much horsepower will this give me? 1 answer
      Its good for NYS 0 answer
      Can these be used on short x pipes 0 answer

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (2) Catalytic Converters

      Tech Specs

      Will It Fit My Mustang

      • Bullitt - 01, 08, 09
      • Cobra - 96, 97, 98, 99, 01, 03, 04
      • Cobra R - 00
      • GT - 96, 97, 98, 99, 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 10
      • GT500 - 07, 08, 09, 10
      • Mach 1 - 03, 04
      • V6 - 96, 97, 98, 99, 00, 01, 02, 03, 04, 05, 06, 07, 08, 09, 10

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