gen vag sensor? if not that could be it as the pattern ones are rubbish.
as above check vag-com, not just for faults but look at the measuring blocks. this can show you what ecu sees from ecu and inlet temp sensors, plus throttle angle etc.
does it take ages to warm up, if sop stat could be buggered. common fault on them, replace the stat housing too as there is liek a peg on there which the stat needs to push on, which often snaps off.
if all the above is ok, try disconnectign the lambda probe. if car is much better then you need a new one
