LPT

My 2002 300RX sat for two months while I was unable to drive. When I started to drive it again, there was significant initial resistance in the gas pedal when first accelerating from being parked. A forceful press on pedal overcame this and engine and pedal responded mostly normally after that. I later noticed that this resistance occurred whenever car was idling, such as when I took my foot off the gas while on freeway or when stopped at intersections or in traffic.
Both I and my mechanic have cleaned the throttle body (which was already pretty clean), lubricated the cable and pedal and checked for excess slack in throttle cable. When I disconnect the cable from the end near the throttle body and slide it in its sleeve there is not any resistance or snagging that we can detect.
Over time (4 months) the initial resistance has diminished (or I have become used to it), but it still occurs when stopped or coasting in idle.
The car idles fine and runs fine.
I have not cleaned the IAC valve (couldn't get screws loose and didn't want to damage them). Could IAC or other things such as cruise control contribute to this stickiness? I only notice when accelerating from idle. I don't know what else to check.