The idle problem returned again. (pretty bad. it was stalling every time I came to a stop.)

I replaced all critical vacuum tubing and spark plugs. (no change problem still occurred)

I cleaned the MAP sensor's electrical connector pins.
This seemed to fix most of the problem. At least, on Wednesday night when I did the cleaning, it warmed to operating temp and stayed idling for 5 minutes. Very steady idle even turning on the head lights and ventilator fan to full didn't cause the engine to stall. It just picked up the extra load.

The drive in to work was stall free and idling was pretty stable/smooth.

On the drive back home, the car stalled once at idle about a mile from work (just about the time it was fully warmed up) and had a couple of times it almost stalled then the ECU caught the problem and opened the idle air control valve.

So, I'm still chasing a minor electrical problem.

I'll have the battery tested. (it's almost five years old. still cranks the engine just fine. but, maybe one of the cells is getting too weak)
Probably, replace the positive battery cable (starter/main positive connection to engine fuse box).
Maybe, replace the negative battery cable (main ground to car body and transmission).