I brought my car into a shop to get the timing belt and balance shaft belt replaced. On returning my car the car runs really loud & rough. (like an a exhaust leak after 3500 rpms). When driving the car it feels like it vibrtates . But I am not sure if what I am sensing is an exhust leak or engine vibration. I am not sure how or why there is a new exhust leak. From what I can tell the leak may be caused from changing the timing belt. They triple checked the timing belt and balance shaft belt and claim it according to specifications. Can anyone give me exact specifications or advise? My car is a 1991 TSI AWD.

Sounds like either the timing belt is tensioned wrong, or the balance shaft is 180 degrees out of phase.

Maybe you could ask them if they did everything described here:
http://www.vfaq.com/mods/timingbelt-1G.html

If it's the timing belt tension, the belt will flap around and make a rattling sound.
It is absolutely necessary to pull it all apart and reset the tension. Continuing to drive could cost you your valves and/or pistons.

No exhaust component is removed while servicing the timing belts.

I think it's probably the bs that's 180deg out of phase. The same thing happened to me and you can feel the vibration a lot more once you rev it past 3k RPM.

Thanks alot guys, that link was awesome!