The type of cams are fitted can be checked by removing the cam belt cover and then you can read the number on the ends of the cams, where the retaining nuts for the drive sprockets are. It will say 569 on the ends of Stage 2 cams and 548 (inlet) and 545 (exhaust) for standard ones. The ECU can be accessed with Protune 2 to see if it is the original locked item or not. I doubt that returning to standard restrictive pipes will damage the engine any more than they would a standard car, just the performance and running will suffer. The owner could always get some quieter Stage 1 pipes and weld the little E tag onto them
