Your car has a 3.2L all post 95 M3 had 3.2 liters. M3's have been having problems with this a lot. I think the nut that holds the gear on the oil pump might have come off. A lot of people have found that their nut is almost off and some have been finding the problem too late and having dramatic and catastrophic losses of oil pressure. Something in the head might have gotten eaten up, have you looked at the car yet? Drained the oil? ^^^ as above what color was the smoke? When you drain the oil see if there are any flakes of metal or something in it.