Ok so i'm gonna be buying the RS-R GT2 exhaust system and also a aftermarket downpipe too but my ? is when u go to the RS-R website and click on the more info for that system, the piping diameter says 80mm (3.15") and arent all downpipes 3" tho? So wouldnt that not work, say like buying a HKS downpipe to go with it? Any suggestion would be much appriaciated Im a newby on this since this is my first turbo car.