There will always be something to confound EDS. I'm with FI, cut EDS out of the loop by fitting a proper boost actuated wastegate -

Wastegate actuator swap for OM602.962?

Hardly matters if you disable EGR now since you're not getting boost anyway.

If you want boost in the meantime and have a responsible left foot, connect vacuum directly to the wastegate actuator so it stays closed. There will no protection from overboost, your left foot is all there is to keep the engine safe. I hope you know what that means.

Two guesses on the oil leak - 1) the front cover of the vacuum pump is loose or has a bad seal, either of which requires a new pump; 2) the big bolt holding the belt tensioner arm to the engine front cover has come loose.

Sixto
87 300D