if you care about warranty (IMO):
- bolt ons and ECU flashes are most critical.
- even electronic mod's are critical, e.g. SmartTop, which allows you to open the roof during driving ( up to a tbd speed you have to configure ).
- BMW started to treat modded cars different, effective 01.01.2010.
remove mods in advance of warranty claims and bring in the M3 to the dealership after clearing tune- or catalysts caused error codes stored in the ECU. e.g. BT cable is capable for this. top speed and rpm will remain in the ECU, only the BMW HQ's are able to access such data, not dealerships.
to remove an ECU flash, the car has to be re-flashed back to stock.