Sorry about the sizing part...just went off of some vendors sites'. Is there a point were you exhaust is too big...for instance Glen was running a 4in exhaust on his car, and it was ridicuoulsy loud..but Im sure it served it's purpose. Where do you draw the line between turbo sizing and exhausts? Is there a formula or calucator I can look at? Im shooting for 400-450whp, dont know turbo sizing yet, so I wouldnt know what size exhaust is best for my setup. I do plan on running of course an aftermarket exhaust manifold which would allow me to keep my a/c, but Im assuming it all comes down to what turbo I choose?