yes the main thrust bearing carries the forward and rearward load of the crankshaft. when dissasembling an engine youll notice that the main thrust bearings are typically more worn on a n engine that was equipped with a manual transmission than one with an automatic. I used to blow smoke all the time and found my thrust bearing to be bronzed after 5,000 miles (yes it was a new clevite bearing) the rest of the main and rods were in good shape.
So in addition to being really bad for the environment, "huffing smoke" is really bad for your engine
so i suggest all of you stop, for the sake of your engine (and our environment)
its also a waste of fuel, i realize that sometimes it cant be avoided (when towing a load or when you want to **** off another driver) but doing it to be "cool" is a waste of money, plus it smells really bad
Matt
Matt