bye bye stock exhaust
 

My stock stang has 115k miles and is a manual tranny GT. Even the exhaust is stock! In short, I'm replacing stock pipes with a Magnaflow 2.5" cat back and an O/R h-pipe on the stock headers. I'm interested in:

Horsepower gain? will I loose low end torque? i doubt I will actually "feel" a difference?

Sound?

the sound will be your biggest gain, or at least the most noticable... It's one of those "ever bit counts"... you might gain 5 HP but you wont feel it... or atleast, I didnt... but who knows... without cats it'll sound so much nastier... (in a good way) and non STOCK mufflers will certainly change your sound too... carefull of those studs on the stock headers.. they've been rusting away for 115k.. they could snap.. and then you'll have to blow them out and put in new ones... might be a good idea to do that anyway... but just letting you know
-as

will the check engine light come on w/o cats?

My 88GT convertible. went from a 15.35 @88mph to a 14.79 @93.3mph when I changed the exhaust. It had a bone stock engine.

You check engine light wont come on a s long as you run the o2 sensors.

Exhaust halped my car ALOT!!

the numbers dont lie.... I havent run my car at the track with or without cats.. so I dont know any numbers.. I hope they are as drastic as those.... the O2s should thread into your Off Road H pipe and shouldnt cause any codes.. newer cars will have 02s after the cats as a check... and most people will get 02 fakers that tell the computer that it's all cool.. even though they ditched the cats... sneaky eh?
-as

Call me crazy, but on one of my stock 88GT's, I threw on a off road h-pipe for the first mod and felt the difference immediately.

the off road pipe mod was my first mod, my car went from a 15.66 to a 15.30 with one installed. if nothing else, a good exhaust system is a great foundation for future modifications