For @#$%'s and Giggles another HP ?

i'd think maybe 10 at the wheels. I just put an o/r h pipe onto my car, mind you i have stock headers/cb. I don't think mufflers do much performance wise, they do wonders on the sound but i think for the exhaust your best bet to gain hp is through the midpipe (hi-flow cats, or no cats) and some nice headers. All the exhaust companies who manufacture mufflers always claim gains of 10-20 hp just from their mufflers which is bs. I'd think in the range of 10 for the midpipe and some more when you put some headers on.