Test drove the Z, the gear shift was very noticeably shaking while stopped. When first taking off in gear, the engine sound normal, then it got LOUD and kind of a wup wup wup noise, almost like a loud fan, worth buying or fix going to be terribly expensive?

 

with your vague crappy explanation, not to mention nobody can tell you from behind a keyboard what is wrong with it.

pay to get it checked out

 

yes

 

Nah, the engine's done. The wups are too short.

 

Could be anything from a crack in the exhaust pipe (inexpensive to repair) to a warped valves (very expensive to repair).