Yeserday I did a light launch with my M6 and ran it hard up to 3rd gear, then had to shut it down fairly quickly with a 3rd to 2nd downshift, but not a hard downshift with loss of traction. When I came to a stop a nice puff of smoke came past my car from the rear. At first I thought it was tire smoke maybe from a short lock up of the rear tires from the downshift, but I got a whiff of it and it was most definitely 90 weight smoke. Could this have just been gear oil burning inside the differential that vented out of the axle vent or is this a sign of something more serious? Ive had 2 of these cars and this is the first time ive ever seen this happen. anyone have .2 cents to put in on this?