2.5" exhaust vs 2.25 or even 2"

@Ccas Good post. Very true. A .5 ET drop is generally recognized as an easy 50hp improvement. And yes! That is a huge gain racers know about.

@Hamerhead IF! Headers are a certainly in the future, I would do both at the same time. On a DIY level, it is easier. You won’t have to cut and splice piping.