nice, I might need to get that checked out then....although I'm not quite sure what the deal is because I have that same problem. First time it happened was in traffic, stop and go for like 45 minutes, it was idling from about 1500-1750. After the traffic subsided, and cruised some, the idle went back to the normal 750.
It happened again when I was doing some AutoX. Idle jumped to like 1800, but kept on doing runs, and it went over 2100rpm after some more.
My last AutoX, 1st run, idle climbed to about 1500rpm, but kept on packing the IC with ice before and after runs, and the idle was at 750rpm again for the rest of the runs.