92 500SL blowing Black smoke heavy @ idle
Hi Everyone,
Have great 92 500SL great condition daily driver, 150,000 miles, well maintained, just one day started blowing heavy black smoke just at idle, this smoke is thick, so far I changed fuel filter ( next to fuel pump ) fuel pressure regulator, several vacuum hoses, nothing seems to change this embarishing problem. Mechanic's do not want to waste time because of year.
This must be a simple problem, it seems it started a little after my transmission maintenance flush.

Thanks for any advice