Hi there.
Sounds very much like they havent got the timing belt on correct. On most Audi engines the cam pulleys are mounted on a taper and so have to be loosened from the cams when tensioning the belt. A quick check to see if it's on wrong is pop one of the belt covers off a bit so you can see the cam pulley. If there's a Tip-Ex mark on the cam pulley and the engine then they have definately done it wrong!
As the tension settles it pulls the timing out if they havent set it correctly.
If they have done it right then check a few bits, such as spark plugs, air leaks on inlet and check the inlet manifold hasn't worked it's bolts lose - they like doing that! Also the inlet manifold has change over flaps inside and they can sieze, if during the belt change the guys have moved these then they could have upset it. You should be able to move the 2 change over valves by hand, although the springs are strong, you will get free movement.
Feel free to call me if you need advice: 01283 548 483 (although I'm not at work now!!
)