How much money do you want to spend? For bigger HP gains I'd go with a catback system. My choice, HKS' Hipers they sound and look aggresive and the pipes leading to the cats are almost perfectly straight. To free up some more HP I'd swap out my main cats with stillen's test pipes. Random Technology also offers a similar set-up. The downpipes are hard to get at but having the transmission dropped would ease in the install. The clutch should also be upgraded at this point. Those people have all their facts confused. Our turbocharged engine with intake,catback exhaust, test pipe, and downpipe can yield 60-80 HP at the flywheel. They told you what could happen to your car's performance unaware to the fact that this is only affects natually aspirated Z's. If your decision is to go only with the muffler section of the catback system and have a shop custom bend the pipes. Make sure the pipes are all Mandrell bent. Some shops bend the pipes and in the process wrinkle the steel causing the exiting air to be turbulent.
