Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Also check that the vacuum hose running to the dump / turbo bypass valve is intact with no leaks as if the dump valve is opening prematurely you'll be losing all your boost
If this is OK then remove the high pressure intake hose after the turbo and have a feel of the turbine wheel - there should be no play radially at all - but a little bit of axial / end to end float is normal
one other possibility is that the wastegate actuator spring has gone soft so allowing the wastegate to open prematurely - if your actuator has a threaded end you can increase the preload on it to see if this improves things otherwise these units are quite cheap compared to a new turbo so it may be worth trying a replacement
New actuator switch and hoses replaced onto new waste gate. New pressure pipe after turbo fitted. Pressure sensor replaced. Appears to be no leakage from pressure hose assembly.Someone suggested that it could be the high pressure valve on fuel pump.What do you think? I have drilled a hole in fuel cap just in case there was a vacuum. Not driven since doing that. Thinking of checking fuel filter to see if it is leaking air.