Just want to add one more thing, I was just perusing the latest EPA reg update from December 2020. They reiterated that epa compliant cats are ok, but they’ve tightened regs on OBD tampering. In other words, only
afaik carb approved tuning is epa compliant regardless of hfc used.
Example, APR has apr plus carb approved stage 1 tines for many vehicles. Edelbrock has carb approved s/c for Jeeps that includes a locked carb compliant tune. I’m not sure anything like this exists for the 370z.
This is good motivation to pick up a z35 since it’s tt from factory and carb approved stage 1 tuning is pretty easy to get for turbo cars.