The issue with the VDC warning in my case was definitely the battery. Even though the battery looked fine, charges well and held the charge....it wasn't giving out enough amps when required. The reason for this was that some of the plates not all of then had failed inside the battery. Therefore on level ground all was fine charging, starting and even checking the current. But when you took a hard corner or drove over a bumpy road the acid would move around in the battery and reduce the contact with the plates in certain parts, thus dropping the power output. Hence LOW current to ECU lots of faults.
The issue with regard to the MCSF could be a few things:
Firstly check all the small pipes leading from the turbo and around the engine bay for small holes. If in doubt just buy a length of tubing and replace them all. They can be bought from any good motor factors.
Secondly, clean your EGR valve and check the pin springs in and out. Also another good test is to pass 12v through it and check if the pin pops in and out. This pin controls the valve open and closed positions.
Thirdly, it could be the over boost sensor on the slam plate which the small pipe from the turbo goes in to. This will need replacing as cleaning it is not an option.
Fourthly, it could be the diaphragm on the turbo which controls the vacuum to the boost valve. This will need removing and cleaning, as they do get soothed up with carbon.
Finally, if all fails then the only option is to remove the turbo and remove all the carbon and soot from the vains in the turbo or just replace itÖ.VERY COSTLY!!
My problem was the diaphragm on the turbo unit; it was completely caked in soot and couldnít release the pressure from the turbo. Therefore causing the turbo to over boost, but once the revs dropped error disappeared and power returned. Obvious now
Follow the steps above before diving head first into buying a new turbo.
Hope this helps.