As stated above, 08e60m5,The dampener is kept intact, which is a crucial part of the engines harmonics as Steve pointed out...a fact is if anyone has been turning wrenches for a long time as I have experienced, when a vibration dampener separates
at the rubber bond and a belt is throne the engine runs rough,the reason the dampener is not working thus the engine is out of sync as far as dynamics, yes the M3 needs the dampener to keep it together.....the M5 retains it ....the only potential problem with under pulleys is they must still turn their accessories at a proper speed in order for them to do their job.