Eric;

When you write that the shop unfortunately "decided to balance the carbs as well", I think what you're telling us is that they may very well have done that to some extent, but from the BT/AT symtoms you've described, it sure sounds like they adjusted your mixture also...and leaned it out to the point of maybe working and sounding fine in the shop (and on the CO meter), but unfortunately not the real world! I believe this adjustment is resulting in the less than satisfactory real world running.

Also, again interpreting your symptoms somewhat, the "noise of a full choke" is really the sound of the engine fast idling as you have the choke fully applied.

The fact is that the guys down at the garage mean well, but they don't really have to live with the car under all of the operating conditions you do....further it is because of this that it is best as an Amazon owner today to be able to make some carb adjustments yourself...and when you get them as you like them, tell the mechanics at the garage to leave these alone next time the car is in for service...only let them make minor adjustments that they need to - like idle.

It sounds to me from your AT sypmtom description as though you might want to do the following (let us know what kind of carb(s) are on your car if you need further specific help):
1. Richen the mixture throughout the entire operating range...this should help stop lean misfire improve "cold response" significantly.
2. Decrease the fast idle somewhat in keeping with a good neigbour policy...this should allow a bit quieter warm-up.

Cherio