This is a more of a I have tried everything what else request.

Customer came in with car fault of turbo boost cutting out after period of boost up hills or under load. The dealer had already changed the ecu, the twin throttle body and egr valve manifold assy 4000.00 dollars.

The customer said he had consulted doctor Google and people were changing the turbo boost sensor, he air temp sensor and turbo boost control solenoid and told me to change those,i warned him its not a good idea to try the scatter gun approach. The parts got changed anyway, no change, btw if you turn the car off and start again the system works fine until you hold boost again.after getting in a auto elec and checking he said the turbo vane position sensor is faulty.new turbo put in,guess what.no change.the dealer has it now and says the glow plugs and relay are faulty and there is a turbo waste gate position fault.they want to spend a grand on glow plugs and relay before going any further.the turbo waste gate fault has always come back no matter whats done, thats the real symptom but i am at a loss to find the cause. I haven't done comp tests or fuel pressure tests.has any one had this before.

PS: the codes are P2562 glow plugs not controlled
and P1351 turbo waste gate unexpected position.

The boost pressure under full boost is 21psi, ive fitted a gauge to check the pressure under load,when its stop boosting you get about 2psi, it will drop off boost and go to limp mode at 5 and 10 psi also, so not just full boost.