Toyota Repair: 90 4Runner 3.0 hot/cold engine issues, air flow meter, vacuum leaks

Question
1990 4Runner 3.0 5spd 125k miles.  No CE light.

During the summer (warm weather 80+), after I have driven the truck enough to fully warm the motor and then shut it off to run in a store, when I return and start it, the motor idles very low, to the point I have to keep it revved slightly to avoid stalling.  After driving for a few minutes like this, it goes away.  Repeats fairly consistently during hot restarts.

During the winter (cool weather 40-), after starting the motor, the engine will stumble if I press the accelerator down too much too fast.  Have to ease away when taking off to avoid a lot of hesitation and stumbling.  After a few miles of driving and engine warms a bit, the problem goes away and stays gone until it completely cools off again.

I think these two issues may be related, but I don't know what gizmo to check first.  FYI - I do get the smell of fuel when motor is first started, but this seems consistent with most all the older Toyotas I've been around.  Also, the small metal "block" bolted to frame behind the grill with wires running to it that I am told is the device that tells the compressor when it is too cold to turn on is corroded apart.  Assuming it only controls the compressor, I guess it isn't related, but thought I'd make you aware of this too, in case it does more than I think.  Not sure if any of this is related, but am hoping you can help.

Thanks much for your help - I've been searching for the culprit to this problem for over a year.

Answer
Make sure that there are no air intake leaks between the throttle body and the air filter, these engines can not tolerate any air or vacuum leaks, the rubber hoses tend to crack so inspect them carefully. Check for any other hoses that may be off at the right side of the engine. If there are no leaks I would suspect the air flow meter and would try another one if possible.