Check your intercooler with a water manometer connected across it. Measurement should be in mmWG in the engine test sheets.
If any higher than the test sheet figure, remove the intercooler core and clean in a ultrasonic cleaning bath if available.
As a guide most medium speed engine intercoolers should have only about 300-600 mm WG across them.
Have seen dirty intercoolers as the problem sooo many times, especially when they "look" clean but inside the core it is a different story and the turbo is blamed.
The only measurement that is important when determining the condition of the intercooler is the pressure drop in mmWG.
Hope this helps