even a stock 370Z needs a Uprev , they are mapped like a turbocharged car far to rich for a N/A car.
Stillen long tube filters help the richness by runnng larger pipes so slowing the air flow over the AFM,s
Changing the Exhaust helps a little as changing to HFC,s will help , but the Uprev finishes everything off.
Stock cars give around 280/290 hub bhp , tuned a car yesterday fitted with HFC,s Y pipe and HKS exhaust finished at 315 hub bhp a gain of around 25+ bhp. and it does another 3 MPG the customer said today.