Hi Jase
Is sound like you have an leak air somewhere,
If you have a air leak in the system then the air via the maf reading will be higher than the actaul air getting in to the combustion chamber, the ecu wil give the injection open time for the air via the maf which causes the fuel air ratio to be rich (too much fuel)
The ecu has a lambda mapnbased on engine speed and engine load, to maintain the correct lambda readings the ecu works in a closed loop mode to constantly change the injection timing so the lambda / air fuel ratio is correct.
There is only a set amount the ecu can cut or add fuel and once this limit is reached the ecu will give a fault code as a warning. If you use vagcom and look at blocks 32 you can see the amout of fuel trim the ecu is adding.
If you want you can pop the car over to us and we will carry out a quick smoke test to find out where you lost air is going. Just dont forget the hobnob..
Nick
