This idle thing seems like a common problem hope my expierence helps somebody:
I have a 2001 Toy Tac V-6.

The past few months the check engine light would randomly come on and go off. Also sometimes it would idle low and almost stall. Also when driving it would randomly loose about 1RPM for 2-3 seconds. Anyway I got it fixed today, it was the throttle boddy sensor, cost $90(parts and Labor)