Thanks Robchriscross, 
Definitely clearing up my auto concerns, 
Ok i know nothing really about the Z so this may be a daft question but why do they need an exhaust upgrade, 
Is the standard exhaust restricted so an upgrade will release more power ? 
 
  
No, it doesn't need it but you will want it. As for the auto box. I didn't want another auto box, but the paddle shift on these are the nuts. Go for it. 
  
Jon