new to this site, have a technical question
 

My 300D 2.5 1991 has been shifting hard, after making some checks, vac pump is fine pulling down to 119mmHg, and runing the engine hooking up the test gauges, i could only get the required vac to the transmission when i plug the line going to the left side of the engine where the turbo boost is and the various acumulators. does any one have a fool proof way to narrow it down beyond that? I do not know what that side of the engine should be pulling normally. and disconnecting and plugging the lines is not going to helpful if i do not find anything major. Any help would be appreciated, have access to a motorized vac pump to run tests.