Anytime someone messes with the ECU there is a chance of things going wrong. A friend of a friend had his S4 modified and then had it chipped...came home parked his car woke up in the middle of the night with his alarm going crazy and his windows going up and down like the car was possesed. The next day he tried to take the car to the dealership but the thing started stuttering on the highway and it finally gave out. He had the car towed and dealership said that it was the ECU that was screwing everything up. Plus, I've heard ECU horror stories from others as well. I'm not saying that ECU upgrade is bad, when done right its great but it carries with it a big risk and also revoked warranty
