Low idle... sometimes?

[el_loco]

2002 750S ie Been giving me a little trouble but running well.  It still pulls hard and seems to rev fine through the RPM range, but I've been noticing what seems like an arythmic exhaust beat at idle, and seems like I'm needing to give it a lot more cold-start lever than ever, and it doesn't idle quite as smooth.  Also when I'm riding and come to a stop, sometimes it's idling at 1200, sometimes at like 700 or 800.  I know Tach's can be a little off, but it's not just the gauge it's the sound and feel, I can tell it's low.  What are some possible causes?