New guy. Been lurking for awhile. Have two ACs - '00 300 4x2 and a '03 500i 4x4 Auto. Got them both new, on E-bay - the '00 in '03 & the '03 in '04. Ride at >7,500' in the wilds of the mtns in WY. Re. smoking. check the airfilter box. There is a LOT of oil in there from the factory. Enough so it will run out of the duck bill and onto the engine. Depending upon on your riding conditions and how clean you keep your engine, oil could be coming from there.