JUST FOR FUTURE REF BANK 1 IS ON PASS SIDE AND THERE IS ABULLETIN TO REPROHRAM PCMFOR FALSE CAT MONITOR CODES

My car (2006 Mercury Mountaineer) does not stall when I am driving under 65 only over 65. But, when I am driving around local 10-60, it just kind of jumps and skips. I have put in GumOut and Lucas Fuel Treatment. Sometimes the engine light will go out and the car runs smooth. I have a code of P0401. Help!

I agree... IAC sounds like the culprit. unless the code you pulled is correct and the catalytic converter is fell apart internally and is blocking the exhaust from exiting properly. That would be very noticeable under driving conditions with things like loss of power and of course the lovely stench it gives off.