I hate to disparage another professional, but I get suspicious when one of my techs claims more than one source for any problem. You know: "it wasn't the fuel distributor but it needed it" type conversation.

"temperature sensor, ignition control module, airflow pot, fuel pressure regulator, fuel distributor, fuel pump, fuel filter, distributor, all new fuel injectors, exhaust system, o2 sensor, and overload protection relay. I also changed out the K-jetronic control module"

I'd give my tech a big "F" on that report card.

Manifold vacuum is a result of engine performance. Other than cam timing it isn't something one can add to other than adding to what is missing. I would add fuel, subtract fuel and see what happens to man vac. I would add timing and subtract timing and see how it effects man vac. (this requires subtrfuse as the timing isn't directly adjustable). I would measure ignition timing to see if its in specs. I have seen a couple cars that ran poorly recently due to the flywheel being installed incorectly after a trans repair. The timing was way off. Cam timing is easily verifiable. Since you have replaced everything concerned except the motor, I would look at how it is assembled.

When I diagnose a problem I first wish to determine what is happening, is it fuel, ignition, or compression. I would seriously worry about your compression if it were taken with any of the gauges I have ever used. That motor should have 150-180psi compression. I didn't mention it because MB v8s never have compression problems. It is probably a gauge issue. The way you get compression problems that far off, uniformly, is with a uniform cam timing issue. Hard to happen with two cams, but might if the crank spun on the chain somehow or if the balancer was on wrong and both cams timed to it.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician