I fully understand that, what they are saying is, is that theres too much pressure in the bottom end of the engine, and there is a vacuum when the dipstick is removed which can be felt when you put your hand over the dipstick pipe. I'm sure that this is down to the vacuum created by the PCV system, but they said they tried it on another GTi, and there was no vacuum.
My argument is that they charged me £1370 for a turbo that they said I needed fitting, when the car still has the same issues afterwards, so I didnt even need that turbo fitting, and I'm trying to find out what the problem is