Thanks to trusty advice from these parts, I think I might have licked the stalling-at-idle problem of the 740. That leaves the 240. It surges at idle, not every time but about half the time.

I've done the following to both cars:
-Removed and thoroughly cleaned the Idle Air Control with throttle body/air intake spray.
-Cleaned the throttle body/butterfly valve in the same manner, though without removing it. Top right bolt defeated me so I left it on and went at it.
-Cleaned out much gunk in the accordion intake hose with paper towels. (Didn't know whether cleaner would wreck rubber/plastic)

That much seemed to cure the 740. And the 240 seems to have improved, but still surges. It drives fine, though mileage seems poorer than usual. Maybe thats the $3 gas talking.

Earlier, I did this to both cars:
-Changed air filter
-Cleaned Air Mass Meter (a miracle cure for earlier 240 stalling problem)

That's it folks. If anyone has something for me to try on the 240, I'm all ears.