Hello everyone, I currently have a S4 N/A that I'm am working on building up for track use. I have finished my brake/suspension overhaul and now a TII swap is next on my list of priorities. My question is what would stop me from putting in an S5 engine over an S4 I plan on going with a standalone ecu? After looking around on the forums I read that most people had issues with the wiring harness differences when crossing from S4 to S5. If I'm going to be redoing most if not all of the engine harness to match the ecu to the engine I dont think it would matter which engine I put in. Any insight or prior experience would be greatly appreciated!

-Jordan