you won't gain much hp, if ANY, from a new exhaust. b/c as Thourun said, the VR4 doesn't require much backpressure (backpressure provided by turbos are sufficient), the exhausts will net THEM plenty of horsepower BECAUSE they need to free up the out-flow of exhaust b/c they have forced induction. The NA, however, NEEDS backpressure, and with a free-er flowing exhaust, you will get some sound, but lose low-end torque. if you just want a deeper, more throaty V8 sound, then go with a test pipe. yes, you'll lose some low-end torque, but you'll also gain high-end hp, giving you a greater top speed in each gear. Plus, there's a savings of, oh...about 700 dollars being that test pipes are just about 30-50 bucks. give it some thought, do the math.