[chittychittybangbang]

Did they remove the transmission? The dogbone pendulum mount (rear lower transmission mount) and all motor mount bolts are single use stretch bolts only. If they get reused they can break. The motor mount is aluminum so if the threads are damaged it can cause the engine to fall down. Make sure the shop uses all new stretch bolts if they loosen the motor mount or dogbone mount.

If not, then it's possible the axles aren't tight or straight.

I don't think there's a problem inside the transmission but it's possible. If you shift into neutral does it change?

 

[chittychittybangbang]

It's pretty easy to remove it if you can jack up the car.

http://www.myturbodiesel.com/1000q_how_to/a4/dogbonemount.htm

You don't need to take it apart if you are putting in a new one, just unbolt, rebolt.

 

[chittychittybangbang]

If you shift into neutral at a stoplight, does it change? If it gets better it's the axles for sure.

If Oilhammer is close to you the best bet is to go see him again. I doubt the motor or transmission mounts are causing the problem. The motorM are new and transM are just rubber pieces and I don't think they are likely to cause idle at vibration. If oilhammer did the balance shaft it's probably not related to the balance shaft.

 

[chittychittybangbang]

This is normal. I don't know the spec for movement but there is a snub mount on the front of the oil pan which connects to a bumper support tube. If this mount is worn it can result in excess movement but I don't think that it's contributing to vibration at idle.

Maybe the Left and Right axles are swapped or the incorrect length causing contact and sending vibration through the steering knuckle? They are different lengths.