1995 E300D Weak Acceleration, Black Smoke above 2500 rpm

[shertex]

So the adventure begins with the E300D I just acquired. Was running perfectly fine for a few weeks. Disabled EGR and the flapper valve next to it by plugging the vacuum lines and disconnecting from throttle linkage, ran even better.

Now, however, at 2500 rpm, when the power is supposed to kick in, I get very weak, anemic acceleration and black smoke out the tail pipe.

Jeremy5848 has been characteristically generous with his time and has given me some pointers. He suggests that the problem may lie with the first flap change that is supposed to occur at 2500 rpm and the double solenoid valve under the IM that controls it. Need to remove the crossover pipe to get to it.

Trying to decide whether all this is above my pay grade....much is, automotively speaking.

Air filter and main fuel filter replaced...prefilter looks fine. FWIW the removal of the prefilter and replacing the throttle guide (and adjustment of the thumb wheel on the throttle cable to get idle right) were the two actions that preceded the problem.

I welcome anyone's thoughts or suggestions.

Thanks.