Hi everyone, I’m looking for some help.

When I’m driving my 2008 Q7 3.0tdi 240hp s-line and I get to a level of boost, the engine seems to start stalling, it looses power and if I take my foot off the accelerator, it will save itself and I can carry on driving (underboost). If I keep my foot on the accelerator, it will stall all the way.

whilst the car is under boost, it drives perfectly fine until it hits the boost level and the car doesn’t bring up an engine fault code.

I’ve already;

Replaced the turbo, Changed the fuel filter, Removed the DPF, Cleaned out the cat and Replaced the air filter.

Has anyone had a similar issue? Any help would be greatly appreciated.

Thanks everyone,

Sean

Could it be the maf? Or turbo actuator? 

I appreciate you've changed the turbo, but if it's a cheap one they can often go faulty quickly. 

I’m tempted to think it’s possibly a sticking/fault turbo wastegate but I’d of thought it would have thrown a code for boost pressure negative deviation or something similar.. Does it do the same thing on idle if you rev it or is it just when under load in gear?