Why are people going to aftermarket H pipes on their 05 and up GT Mustangs? I thought I read somewhere these exhaust systems were good to like 400-450 H.P.? Am I wrong? And will you get any noticeable sound difference from one H pipe to another?

 

OR H = no cats = more sound, less weight, more H.P.'s

 

Oh, and a much better smell.

 

Thanks, I didn't realize the cats were on the H pipe.