for a turbo car, the larger the better normally. a 3" pipe is good, and is complimented with a hi-flow intake (stillen, jwt or HKS) the muffler basically determines the tone of exhaust. if you REALLY want a difference, get 3" test pipes with downpipes :^) this is just a kind of guideline. now do the research for brands...the HKS super is a 3" exhaust and is real nice :^) try it, cant go wrong -Dan