Problems with E320 BlueTec

Problems with E320 BlueTec

Purchased my car new in 2007.  I love this car: however, in the past year I have had some very expensive
problems.  Bear in mind, that I have always used the dealership for all services as required.
At 60,000 miles, had the transmission replaced; at 69,000 miles, had the inlet port shutoff motor
and linkage replaced (8/15.2012).  Right now, it is in the shop having the manifold replaced due to
carbon deposits.
Each time the symptom was the same:  From a stop, car will only accelerate to 15-20 mph.
If I turn off motor and re-start, it will drive fine.  Tech says it is not the CTU.

Help!!  This is sad.