my friend may be trading in his 07ss with stg 2! can i just swap ECU's with or will be both have to get reflashed?
him back to stock and me back to stg2!
i assumed i could just swap my stock ecu with his reflashed ecu??

 

And what is that going to do? Stage 2=hub+pulley+belt+injectors+tune...if you don't have that the pcm is going to make your car run stupid. All pcms have a vin written to them, so if you swap them he'll have your vin and you'll have his vin. The short answer is you can but not if he wants to sell his car; one of them has to be reflashed with the car's vin.