My Z runs great. It's not tuned but I did not have any major problems with it at all (engine wise), no misfires, engine runs great, no boost or vacuum leaks, the engine is definitely healthy and maintenance is up to date. When getting on it I always keep an eye out on all the gauges and make sure it doesn't overheat. I love the sound of the turbos and engine at high RPM. Never have the radio on during those times :-).