My 2 cents worth:
I have one Legacy and one Vision engine that have smoke unit "buzz" and one is a steamer (UP 9000) and the other is the original Vision GE Evo. The latter was my only completely dependable, problem-free Vision Line engine until it developed an annoying squeal when the smoke unit fires up. I put that down to overfilling with smoke fluid (and the model sitting on the display shelf for some months), which I understand can affect the bearings/impeller but I'll gladly be corrected if I am wrong. I'm loathe to open this engine up although it is long out of warranty. I have got some Megasmoke "Eliminator" and I will try that before I think of trying to service the fan motor as I understand that this product can help clear up minor fan issues.
The steamer could probably benefit from the treatment Eric Siegel posted a video about but again taking it apart is pretty daunting.
