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To drop cats or not to drop cats

3K views 32 replies 14 participants last post by  stlwagon 
#1 ·
Hi everyone... I'm new to the Mustang forums. I have a 2005 Mustang GT Redfire 5 speed. I have just installed a K&N FIPK 57-2565 Cold Air kit and Flowmaster American Thunder axelbacks. I'm contemplating dropping the cats in favor of an off road H pipe. What issues should I be aware of with regard to the MIL sensors for the O2 CAT sensors? I would like to do a bolt on/off pipe, as I live in an emissions testing state, and will need to swap them out for testing. Look forward to recommendations
 
#2 ·
Do you have your stock heades on? If so just switch it back when the time comes for testing.
If you drop your cats you'll get a "code" because of it. That can be stopped by getting tune.
 
#4 ·
I would get a SCT tuner from Doug at Bamachips.com and that way you will get a lot more power. You will also get free tunes for your new bolt ons.
 
#6 ·
I don't think it's worth it to remove your cats. You will make better power on other mods. Not only that all you will be doing is making our air dirty. Our cars have pretty good exhaust for a factory vehicle. The only real gain in exhaust would be to install long tubes with cats. There you will notice a nice increase.

I'm "green" and I'm making more power than guys here with off road exhaust. Proof positive you can make clean power.

My .$02
 
#7 ·
I took the cat's off ( alittle gain can't tell but I like the sound better). It kinda dirty's the air but it's no worse then seeing a 18 wheeler blowing black smoke everywhere!
 
#9 ·
I've also considered hi-flow cats, as I'm not against preserving the environment. I'm looking for a bit more sound out of my Flowmasters, which an O/R H or X will give me. You folks who have programmers/tuners, any recommendations such as from BKid there are more than welcome. And thanks for the AFM welcome!
 
#17 ·
I have always run O/R pipes on my Mustangs before I got my 07. I'm glad the shop I get my stuff from started one up with O/R pipes on it for me so I could hear it before I pulled the trigger. WAAAAAAAYYYY too loud. And this is coming from a guy who Roadraces motorcycles, rides a turbo Busa with no exhaust and likes to shoot guns. Oh yeah, I like Slipknot too:D

I would suggest you listen to a system with no cats before deciding to ditch them. My $.02
 
#20 ·
i personally am running my 02 GT with flowmaster 40 series mufflers and a summit o/r h-pipe....personally i love the sound of it...its pretty throaty sound..i didnt order mil eliminators when i installed my pipe..and 3 days later my sel came on...its only been on for a little while...and i am pretty tired of seeing the ****...so word of advice...if you do go with this setup...order mil eliminators...performance and drivabilty wise..the code doesnt affect it....as for performance..i notice a little more tourqe off the line...:).....well i hope this helps ya...good luck with your choice!
 
#26 ·
I would get a superchip flashpaq tuner. Just log onto the website, click on all the mods you have on the mustang, and they will provide a tune immediately for download via USB right into your tuner. Then upload it into your mustang and your good. I have one and it is a big difference. YouTube - 08 Mustang Exhaust Flowmaster Driveby
Found this on you tube. american thunder axlebacks with summit racing o/r H pipe, no cats. :bigthumbsup
 
#29 ·
The ones at brenspeed (mil eliminators) do not work on 07+ stangs. I know because I bought a pair for mine without researching properly. Ended up having to sell them, they will work on 05-06 mustangs according to bresnspeed.

I've been running an OR H and it sounds great. It will be loud, be prepared to have trouble hearing your wife/passenger/girlfriend while you're driving.. more so... lol.
 
#30 ·
I stand corrected, sorry about that. They told me when I bought them that they were a universal design that worked for any mustang built after 04
 
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