2002 Honda Accord Low Idle at Temp

Hi all! I have a 2002 Honda Accord 4cyl. I recently had the transmission rebuilt. After i got it back I had an error code for downstream O2 sensor which went away after I replaced it. Then I had an upstream O2 sensor code that would come and go intermittently. Since replacing the downstream fixed that issue I decided to play it safe and replace the upstream. I was still getting the code off and on (P0131 – Low Voltage). I tested the wires and was getting a pretty constant 11.x Volts. I replaced the harness plug as some of the wires were a bit loose. Still getting an intermittent P0131 code. I tested for vacuum leaks (none). Whats more odd is that at operating temperature and while stopped I periodically have a very low idle. It seems to get worse when the check engine light comes on for the P0131 code and gets better after I clear it. I’ve also noticed that the RPMs will go down when the A/C kicks on, the brakes are pressed hard, attempt to roll down the windows when they are already down, etc. I’ve tested the battery and alternator and all that checks out. I also replaced the cap/rotor, plugs and wires. Could all of this be related to a faulty AIC valve? Could my new upstream O2 sensor be bad? Any other suggestions? Other than the low idle at temp while stopped and the intermittent check engine light the car runs and drives excellent. All comments and suggestions are more than welcome. Thank you!