94 es300 118k.

just bought it. Stinks on hard acceration. Smokes while idling. smoke is coming from behind/under engine. Smells kidof like a burning fluid, but nothing obvious. Not gas or burnt oil smell. not rubber or plastic. I can't find any leaks. It's not losing any fluids. Mechanic said it may be a clogged catalytic converter. Someone else said it may be running rich. O2 sensors were replaced 40k ago. Peformance seems to be OK, but I just bought the car so I don't know what it's supposed to feel like.
I just replaced plugs, fuel filter and thermostat. The plugs looked excellent.
It kindof surges on hard accelration. Not horrible, but noticeable. related?


ideas?

many thanks.
- Nate

check the valve cover gasket. I have the same problem with the smoking while idling and my friend which is a lexus mechanic says its a commmon problem with all 1992-1996 es300s.