has anyone dyno'd a car with just an aftermarket muffler and not a cat back system? after wasting about $200 getting a ractive 'mugen' copy muffler and getting it installed i read that mufflers alone won't help out with backpressure/ better flow. is this true? the muffler is twin loop and has 2" piping and i got axle back 2" piping, my stock exhaust is ~1.9" (ex) so i didn't see any reason to get 2.25" piping if the muffler would be a bottleneck. dont know if the butt dyno is lying to me or not. could i have seen any gains?

 

either way, you wont feel much of a difference with just bolt-ons