Originally Posted by KmndntKlink
I'm in the same boat, seriously considering an ESS tune, but their tune is reversable, so it would put all of these back in pilace. If you reflash stock before taking it in, wouldn't bmw not know? Or is there some log that records when the engine goes above rev limit & speed limiter that isn't wiped with the flash? Would really like to know how this works if there's any bmw techs or car engineers who know how ECUs work.
I'm probably going for it anyway tbh, it seems like a great mod to really trim everything up for not much $$$
Flashing it back to stock before taking it to the dealer is a waste of time (unless you're dealing with a catastrophic issue and they had clear indications that there may have been 'tampering'.
A proper tune will not cause fault codes or show any indication that the file is modified.
Putting it back to stock does not modify the freezeframe data, it is stored in a section of the left processor that can not be modified without opening up the DME. The only reason you might want to flash to stock (or flash to a different revision of the tune) is to turn the secondary air pump back on. But most dealers wouldn't notice that the car wasn't louder on startup.