unhealthy growl at steady RPM

My 1981 KZ1000LTD started doing this today when i got off the interstate and went home. Whenever i hold the throttle slightly open to maintain a speed, it seems to have a very unhealthy growl, much like how a motor sounds when its running out of gas. Like one cylinder is not firing. But when i open it up just a wee bit more it smooths out... but then im accelerating and i dont want that I did check the oil and found that it may be contaminated with gasoline. There was smoke coming from the pcv tube that goes into the crank case (i have a little filter on there from a chevy 350). Not lots of smoke, but like it was hot in there. The oil was low and very fluid like it wasnt as thick as it should be. Any ideas on what might cause this? I was almost thinking that the carbs arent synced together and one butterfly is shut more then the rest.