1993 Lexus SC 300 Sensors or engine?

Engine Mechanical problem
1993 Lexus SC 300 6 cyl Automatic 200k miles

My car has thick white clouds of smoke from the tailpipe when its running. It doesn't overheat, and the smoke smells like gas. I was originally told it may be the Mass air flow sensor, and I replaced that but there is still smoke, not as much but still more than usual. It idles low, the check engine light is not on and prior to replacing spark plugs, there was oil inside where the spark plugs were. Does any of these symptoms point to a particular problem? I have clues that it could be a couple things but every time I think I may know what it is, I find a reason why it may not be what I originally thought. Please help, I'm so confused. I have talked to at least three mechanics that have looked at the car and I am still unsure, maybe, they weren't the best people to consult since I replaced the part they suggested was the problem