LOL! You actually remember the compressor cut-out switches!
This problem doesn't really fit an oxygen sensor problem (too quick) but with one exception... You may have a fuel adaptive cell that hasn't been updated from when you had been using E85 earlier, something that you pass through only in limited circumstances such as tip-in with A/C on. It's a stretch, but I can't discount the oxygen sensor code (whatever it was... several flavors). They don't normally go away, rather an oxygen sensor tends to decay as it ages, getting progressively less responsive over time. If the Oxygen Sensor Monitor picked up a failure of some sort a few months ago, it's probably best that the sensor be replaced, whether it's the cause of your off-idle sag or not.
I think that's what I'd categorize it as at this point... a sag on acceleration rather than an outright misfire. Does that sound right to you?
Sags are caused by something common to all cylinders in most cases, things like fuel mixture, ignition timing, etc. Your mention of TPS is rooted in fact, but isn't common. You may have a TPS issue, but it shouldn't be A/C dependent. Failures of the TPS often (but not always) set a code and turn the CHECK ENGINE lamp on. I'd expect idle fluctuations and odd transmission shift issues to go along with an erratic TPS.
EGR should be considered, although this would also be an unusual manifest of EGR system failure in this year. Easy to test, disconnect the vacuum hose leading to the metal portion of the EGR valve, or disconnect the hose back at the intake manifold. You'll see the hose coming off a vacuum "tree" near the throttle body side of the intake, snaking its way up to the general TB area. Disconnect it (leaving it open is OK for quick test), then do an A/C ON off-idle test to see if it changes anything.
EGR is normally disabled for a minute or so after engine start anyway, but your EGR backpressure transducer solenoid (I'm not kidding..) may be flowing at all times by default. Disconnecting the vacuum source positively prevents the EGR from opening after that point.
Last... and I hate to tell you this... do a battery disconnect of several minutes to clear PCM adaptive memory. You'll be starting over from square zero on all adaptives that way, but any codes stored as either full or 1-trip failures will be erased as well. It might be wise to see the AutoPro boys one more time before whacking the memory.
With all adaptive cells back to zero, any oddball adaptives will be gone as well. If this immediately cures your off-idle sag, I'd recommend the upstream oxygen sensor.
Write back if you have any questions or problems, John. I'll be glad to help.