Since this occurred "at a 12K service", I would check for problems created by the service. UPDATE - I just reread your post and it indicates that it started around the time the 12K was due and you hoped that the 12K would fix it, so, this is probably of no use, but, since you are out-of-warranty, they are easy things to check (once the skins are off).
First, check all of the vacuum and vent lines and make sure that they are not pinched or that one came loose. Since they had to remove the tank to replace the air filter, there is a high possibility that they left a hose disconnected or pinched.
Some have noticed a major increase in gas tank pressure when the vent line to it was pinched.....try opening the fuel tank lid while it is idling bad and see if it affects your idle speed.
While you are under there, also check all of the electrical connections in this area. The fuel disconnects are idiot proof as far as putting them on wrong, but they are fragile if a tech puts any sideways pressure on them while disconnecting or re-connecting. Inspect these while the skins are off.
Other things to look at are pinched/binding throttle cables. One test is to engage your cruise control while going down the road. Does the bike surge up or down in speed a few miles per hour or is it a smooth operation? If it surges, check for binding and/or adjustment of the cruise control throttle cable (the one towards the rear of the bike). Both cables should operate freely and not stick.
I am assuming that it still starts and runs OK/normal since you didn't say that you were having other problems (hard/longer starts, stalls, missing, etc.). If you are having any of these (or other) problems, let us know since it may direct the trouble shooting elsewhere.
Last edited by htheater; Dec 18th, 2005 at 8:01 am.