New Wastegate/Boost solenoid valve for all 6.5 TD's 94-97.
This valve controls your wastegate actuator valve which controls boost. Replace your defective solenoid and restore boost pressure. This is the most common item of failure in the boost system.
The vacuum pump creates and supplies vacuum to the solenoid, which in turn controls vacuum to the wastegate actuator which opens and closes the wastegate valve. You should have a minimum of 15 inches of vacuum at the wastegate actuator. If not check output at the vacuum pump. Should be 20"+ at the pump. If ok, you have either a cracked vacuum hose or a bad solenoid. The solenoid is located on the drivers side valve cover. It is the front most solenoid of 3 (other 2 are for the egr valve) if an L56, or the only solenoid if an L65 (HD). An easy 5 minute fix to lost power, heavy smoke on acceleration, and poor mileage.