Lean idle. Rich cruise.

If you are cruzing at 3k rpm I would guess you are activating the boosters unless you have blead off a lot of signal. Try crusing at at lower speed (~2K RPM) and see how your AFR reacts. You need to figure out if you are tuning the Idle circuit or main circuit or a combination.
Other than the AFR gauge showing lean/rich- what drivability issue are you trying to address? (Stumble, plug fouling, just don't like how it smells etc?) Like a lot of other people said, the AFR gauge can be erroneous at idle due to the overlap.