OK, So I bought my 2007 GT a few months ago from a dealership. I did some research on some minor mods, found out it had a Hurst shifter installed, tuned and new exhaust from Cat back.


Turns out they just installed new pipe all the way back with no muffler.
My question is how will this effect performance--good or bad.

 

Very little if any at all.. If the new pipes have mandrel bends as most aftermarket exhaust components have, you may see up to an additional 2-4 RWHP but I wouldn't count on it, especially with the factory cats still in place..

I'd recommend either upgrading to an off road mid-pipe or better yet upgrade to Long Tube headers with high-flow cats if your looking for better airflow and noticeable difference in RWHP.. Mufflers on the other hand only provide better sound over stock, but don't offer any performance gains whatsoever..