That could be a number of things bud, however it seems that this could be Air/Fuel related.
Unfortunatly that could so many things I.E..
* Coil packs.
* Spark plugs.
* Lambar sensor before CAT.
* Lambar sensor after CAT.
* Temp sensor.
* Boost leak.
* Faulty DV.
* Faulty CAT.
* Faulty injectors.
* Faulty MAF.
* Leaking injector seals. (Would also come under boost leak)
* Leaking injector seats. (Would also come under boost leak)
* Rocker cover gasket leak. (Would also come under boost leak)
* Inlet manifold gasket leak. (Would also come under boost leak)
* Throttle body gasket leak. (Would also come under boost leak)
* Faulty throttle body.
* Dirty throttle body.
* Faulty sensor located directly bolted into the inlet manifold just next to the TB.
* Faulty MAP sensor located in the intercooler.
* Faulty AMP thingy thats bolted into your airbox (Not sure is this only applys to AGU engines).
* Big carbon buildup, use "Slick 50" to help clean it up. Only use it once every 4000 miles.
* Or if you have been using an induction kit ensure you haven't been using an "oil coated" cone, these kill MAF's.
You can clean a MAF using eletronic contact spray.
However the best thing you can do is scan your car with vagcom first.
