If you are looking for actual parts or "features" to add to a real BMW M3 (G80/F80/E92), these are the most popular upgrades according to enthusiasts: Performance & Tech ECU Tuning
Some popular challenge mods for the BMW M3 include: bmw m3 challenge mods
Intakes that aren’t sealed, lightweight pulleys, and most “stage 3” tunes without supporting fuel/oil mods. If you are looking for actual parts or