Hey, i just bought my bike a couple weeks ago from a friend, and i took it to a shop to get some stuff fixed on it. They fixed a gas leak and something with the petcock. I didnt get the petcock replaced becuase he said as long as i keep the knob pointed up when i ride and down when im not, itll be fine. When i got it back, it would idle dangerously low when i was at stop signs and stuff, and a few days later it got to the point that i cant even ride with out the choke on. Now, it will stall nomatter what unless i have a little bit of throttle on. Its also really hard to start in the morning, and yesterday wouldnt start at all. I hooked it up to a car battery and it started fine and ran at a healtier rpm than usual too. About 5 minutes later its back to normal, not working well... Is this a battery problem?
How long are you warming it up for? Mine takes about 30 seconds full choke, 5 minutes med choke, then I ride with the choke on for about 3-5 more minutes then no choke. GS's are notorious for warming up.
Go for a long ride, then adjust your idle speed to 1100 to 1200rpm
Its not likely to be battery or electrical. ducati_nolan suggest adjusting your idle speed with the engine hot, i had similar problems with my second bike and it worked for me, you adjust the idle with the little nylon knurled screw gismo...
(http://www.bbburma.net/CalPrice/idlescrew.jpg)