Hard to say whats going on, if there was something wrong with the engine mechanically then you'd know about it, after owning a mk3 vr6 i can tell just how good a vr6 engine is running just buy listening to it

It could well be a faulty mass meter or a fault in the wiring..
You really need vag com because even though snap on is top stuff it may lack the actual technical vw dtc fault codes.
It's a joke how much garages charge, but hay many people are willing to pay for it, people in britain put up with alot of crap, they don't call it rip-off britain for nothing now do they!
Just look at the petrol prices we have been conditioned by years of high prices that now the british just like paying £1.25+ for a litre.
I'm scared as to what the future holds for us.