I'm one to diagnose stuff, cause I love figuring things out, so here it is: at school here there is a 300zx (pretty damn clean one at that!) that has dual dual-tip exhaust, and I'm curious, when it revs up there's a popping sound almost like a machine gun. and I can tell it's coming from the exhaust, not from the engine. ever since I've seen the car, it's had that. I'm curious, could this be from the exhaust being too restrictive, or possibly too open? I'm not sure if it's the twin-turbo, or if that's all they came in for that matter, but I was wondering if that would have an affect on it. could it just be the exhaust? I dunno, just curious, plus I'm bored. What do you guys think?