I can only imagine how frustrating this has been! I had an '87 Suburban with a 350 and TBI which used to do the same thing. Every so often it would stumble and set the CEL, until I shut the ignition off and then it would be OK until the next time! When I was dropping the tank for the 3rd time, I noticed that the fuel pump holder/pick-up and been modified by some previous owner to use an assembly from a pick-up truck, which at the time must have been easier than spending the $200+ the correct one cost me. After that I had no more problems, at least FUEL problems anyway!
One other "weird" thought - does this fuel pressure/vapor lock happen more frequently in hot weather? I remember reading that some of the folks who used the Suburban to tow the Airstream trailers complained about that same problem. Their solution was to paint the bottom of the fuel tank white to keep road heat away from the fuel! It worked for them!!
Wish I could be more help! My only Suburban problem is the terrible gas mileage @ $3.50 a gallon means I don't go out a lot!
Lew