Hey I am looking at getting JBA longtubes for my 07 gt and I was looking at the sizing of the collectors and was wondering if there is a difference in horsepower gains between the 2.5 inch collectors and the 3 inch collectors? I can get either corresponding h-pipe. If it matters I am getting a SLP loudmouth exhaust which has 2.5 tubing.

 

Technically the 3" will have a slightflow advantage, assuming the 3" carries all the way back to the "X" in the X-pipe. However, I doubt you would see a noticeable difference unless you are pushing some seriously high HP (supercharger or nitrous).

 

Thanks CrazyAl. I dont plan on anything big so 2.5 it is.