Originally Posted by drz
Could be you need anew air filter or the intake has a rip or hole in it (check this first). Also, your belts could need replacing. The best way to diagnose this is to have someone rev up th e engine while you listen in on the engine bay.
what this person said, when engine is cold take a look at your intake boots get in there with your hands and feel, the small part on the lower intake boot is most likely cracked.
2001 330I, sport/Premium/cold weather package, short shifter with M3 weighted knob, clear corners, 60 led angle eyes