I had stalling issue with my 83,000 mile 91. After replacing a few underhood parts mainly due to old age and peace of mind, I did the plugs, wires, new distributor, new injectors and TBI rebuild, CTS, etc, etc, I found a minimum idle speed adjustment. There are a couple of procedures for it, one in the repair manual and ones on the net.
The IAC controls idle speed "most" of the time just fine. The "minimum idle speed" is set at the factory to a bare minimum but just like a carburetor, it may need adjusting. It's a screw stop for the throttle linkage just like a carb. Mine was so out of adjustment the throttle blades were sticking in the bore and I had to push hard on the pedal to take off from a stop which made the truck lurch somewhat. Sometimes the IAC will lower the idle speed a bit too much causing a stall. A new replacement IAC for the new IAC did not help mine. That min idle speed adjustment fixed my stalling issue.
Your scanner pic shows 662 rpm and that's good but it doesn't stay at that. Mine idled normal "most of the time" but dropped lower as I sat in gear with foot on brake for a few minutes until it finally stalled. My throttle body is tight as in no vaccum leaks, fuel pressure is 11 psi, on an all stock
91 350 truck. A few full turns of the idle speed screw solved my stalling issue. I did those turns a 1/4 to 1/2 turn at a time to ease up to that just right spot. Also the throttle blades no longer stick in the bore at idle. Maybe that helps you.