I have a 2002 WRX with a Prodrive Stage 2 performance package that include an ECU reflash. I need to return the car to stock for sale/trade in purposes. I have a friend who will buy the whole set up from me. He has a 2004 WRX. According to Prodrive all the hardwear will fit. Does anyone here know if we can simply swap the ECUs in our cars or are there significant incompatibility issues that I should know about. I'm sorry if this question has been asked before. I did a search but couldn't find any relevant information. Thanks for your help.