Rally hit it.

Those are relatively simple cars.

Look on the intake manifold and find the bundle of hard plastic vacuum lines. Look carefully because they're so fragile they'll crack if you look at the wrong.
A simple little crack in one of those lines or it's rubber boot will bleed enough air pressure to send the engine into overboost.
Find the solenoid pack on the strut tower. One of those will be the barometric solenoid. The wastegate solenoid will be in there too. One line will continue inside to the MAP sensor.
It's critical to have GOOD vacuum lines going to those devices. The same goes for the wastegate itself.




Most of the problems I had with my Shelby Chargers were vacuum related.

Check with GDonovan. He is the resident 2.2 turbo guru and knows more about those engines than the rest of the Moparts members combined.

Here's an 89 turbo II vacuum diagram. Your car should be similar.



While you're fiddling with the car, check the fuel supply and return lines going between the fuel rail and the fire wall. They can become brittle over time. The last thing you want is a leak in a high pressure line spraying fuel on a red-hot turbocharger. Be sure to replace them with EFI rated hose.