2002 Volkswagen Jetta

First of all, tell me what kind of oil you've been running in your engine? I want you to remove the Hoes from the cold side of the turbo and start it up and tell me if it is spinning, have you checked your air cleaner to make sure it's not restricted? The only other thing you could be is the wast gate, it is vacuum activated, and it may be bad, or you have a broken vacuum line to it, or maybe no vacuum at all, that will cause it to stay open all the time, and not build up any turbo boost.

The next thing to do is check the turbo boost, do you have a boost gauge on your car? If you don't you will need to get a gauge and there should be a plug on the boost side of the Turbo so you can check the boost, you said "seems like actuator is good" we cannot be speculating here, it is either good or it isn't, take a vacuum pump on the actuator, pump it up to make sure its holding vacuum.

Okay I'm glad that out of the way, now the next issues, you did not tell me is how many miles on the vehicle, you did not tell me what kind of service work you've had done? Fuel filters etc. Is this a diesel or a gas? Answer my questions, so I can be able to help you.

Now you are racking my brain, you stated "The turbo boost is ok" so the only other thing it could be is injection pump, timing belt or the oil "I use castrol syntech oil" is that castrol syntech oil approved for diesel engines? I have over 75 diesel vehicles, I do not use synthetic oil in them I only use the approved specified diesel oil. If Castrol does not specify on the back of the bottle that it is for diesel engines, I'm afraid you've ruined your engine. I am going to the part store now to check up on this Castrol synthetic oil.