The 1.8T are prone to oil sludge which blocks the oil strainer in the sump causing the oil pump to struggle to push good pressure to top end of the engine....
If it is this causing the problem fingers crossed youve caught it in time... other wise you could be in for a big repair bill .
Is the red oil can light showing on the dash at all??
Is the seller of the car a trader or private seller ??
Have a look at this thread with similar problems reported
http://www.audi-forums.com/general-a...ng-engine.html