I doubt your computer is blown, in your first post you said your were losing vacuum. Did your independent shop tell you that?

The boost control system on the 2.5 turbo will default to a no-boost condition if there is no vacuum available to run the actuators for the wastegate, EGR and intake manifold flap. Your problem could be as simple as a vacuum leak somewhere - if you have no vacuum find the leak and fix it.

The boost control system on these engines is impressive - it builds boost much faster than the manual system on the OM602/OM603 set-ups, at least the ones I've driven. It makes the engine seem much more powerful than the rated 121 horsepower.

If you wanted to replace the computer operated system I would try to find the intake/turbo/wastegate control for an 87 190D 2.5 turbo. I'm pretty sure these setups were not computer controlled, trying to jury rig something to operate the three transducers on your car would be complicated.

If you want to try the approach outlined in the previous post don't try to use the intake manifold as a source of vacuum - this will work on a gasser but your car will not produce any vacuum in the manifold because it does not have an intake manifold flap.

Tim