Theres probably already a thread on this but I cant find it anywhere only on the FD forums. If I street port my 1987 mazda rx7 sport would i need a tune or would I be fine with stock tune.

 

I wouldn't. porting your engine essentially means your changing the timing of the intake stroke so you'll want an aftermarket ECU to get the most out of it. If its a small port you might be able to get away with it, but if its anything serious, you'll want more control over timing that the stock ECU doesn't offer.

 

You'll never make enough power with the street port to necessitate a change in tune. As the FC ECU is an air metered system, it will automatically compensate for the higher airflow.

However depending on how far you want to go into this, you would see significant benefit from a tunable ECU, like a standalone. The FC ECU is pretty crude, and you'll gain both power and fuel economy by re-tuning the car. Now whether that is worth the high price is something you need to decide.