These 350Z / G35 Stainless Steel Test Pipes with In-Line Resonators replace your factory catalytic converters, letting all the exhaust pass through freely, but not the noise. The full stainless straight through converter replacement, but with a stainless exhaust resonator welded in-line. This gives an equal amount of flow, but without the raspiness. The exhaust note will only be slightly louder then stock, and have a slightly deeper tone. We have these on our ACP project Z, with GReddy Twin Turbo, and gained 37 HP! Must for FI application Stock 350Z and G35 can expect 5-8 HP gain These are test pipes w/ resonator NOT Cats We have them listed in the CAT, Catagory but again our a test pipes w/ resonator ** These pipes replace your factory converters and are NOT street legal, for off-road use only**