GT Mustangs

Senorjizzy · 10-11-2009, 09:31 PM

my cats have been rattling horribly (worse everyday), and have just ben thnking bout getting them cut off. but im going to replace them. should i buy stock? or go aftermarket?

2nd, while im getting this work done, ive planned on going with an H-pipe and some sort of flowmaster exhaust setup. ive been told that with 2.5 piping ill lose back pressure. so what mods would make up for this loss in power?

id really appreciate everyones 2 cents. i need this bad.

sonicpony03 · 10-11-2009, 11:07 PM

If you're gonna go with new cats, I'd look into hi flow aftermarket cats. Pypes, Magnaflow, SLP, they all offer hi flow cats for our mustangs. This way you're only stuck with 2 cats and will still be emissions legal.

The 2.5" piping is standard on pretty much all aftermarket systems. You really won't lose that much backpressure...or torque, maybe 1-2 ft.lbs. A set of under drive pulleys would recoup that slight loss in torque. They are cheaper than the 99-04 udp's, so I would consider them for your car.

**SpectorV** · 10-12-2009, 07:15 AM

after owning 2 v6s I would NEVER cut the cats off, they sound bad enough with just a catback up high. Down low they sound fine but up top, not so much. I would pick up a take off Y pipe with all the cats in good shape and put it on.

Senorjizzy · 10-12-2009, 01:00 PM

wow i never thought of that. but how owuld i tell they are in good condition? anything i should look for specifically?

SaturnMan8227 · 10-12-2009, 05:34 PM

Well first off remving the cats is illegal. Depending on your state you could geta fine and not pass an emissions test. With that said I would get some magnaflow high-flow cats. They are obdII compliant and should be street legal. You probably won't notice any loss in hp or tq if you go with a 2.5in pipe and mufflers. Depending on what sytem you buy(custom or pre fab) you might actully gain hp and tq.

lowflyn · 10-12-2009, 07:27 PM

Just stick with 2 1/4 piping. It'll flow any amount of power you are wanting to put down and it's cheaper than 2.5.

And on a V6, keep the cats. I had an offroad x pipe on my old v6 and it was just bad..

sonicpony03 · 10-12-2009, 11:51 PM

I'm pretty sure he is going to replace the cats somehow, that's what he said in his op. He wanted to know if he should go with stock or aftermarket cats.

I agree with lowflyn on the piping. The easiest way is to retain the 2.25" piping all the way through. A takeoff GT catback will retain the 2.25 piping, though they can be harder to come by these days, I'd check a local salvage yard for a GT or cobra. I don't know if exhaust shops fabricate 2.25" piping, I'd imagine so, but I haven't been to one in a few years