Plumes of smoke from exhaust during throttle
So recently I've noticed that during idling in my driving that plumes of smoke (kind of grey) blow out from the back. It'll only occasionally do this. I had my tired changed out today at the dealer and reported this problem. After the alignment and test, they also said they experienced the smoke but couldn't tell me what it is and that I should bring it back tomorrow to get it looked at right away.
I hope something like this is covered by my CPO and extend. maint.
Anyone experience smoke on throttle?
80K '06 x5 4.4