I ran a single 4in (3in DP's to 4in Y to 4in back to gutted stock muffler). Had no clearance issues (at stock ride height on a G coupe).

couple things to consider. Are you running open dump WG's or recirc? Recirc require more flow through the exhaust.

Tom

 

^^I am running Open Dump WG's

 

^^ OK well i got an update. While i wait for my AAM 3" Dual Exhaust to arrive i have given my AAM 3" to my friend and right now using the knock offs HKS 2.5 dual exhaust just for $hits and giggles till the AAM arrives and i felt the difference instantly. Boost comes a lot quicker and the car feels a lot better.

 

I am running Fast Intentions 3" test pipes mated to Fast Intentions true dual 2.5" exhaust and I will also be running the GTM TT kit. Exhaust should flow just fine, I may add an x-pipe later on for more even flow but I don't think that the exhaust will be limiting much if at all.