GRRRR... fuel problem as well

Just thought I'd add a thread to an already growing epedemic of 4.3 fuel problems. All my problems as well have started since running low on fuel. After getting gas, within 20 miles I no longer can drive my new (to me anyways) 1990 astro rs. We have so far replaced or rebuilt the following: fuel filter, air filter, o2 sensor, fuel injectors, fuel pressure regulator and tested the fuel pump. I then hopped on the ol' faithful internet and have came to the conclusion that we could try 100+ things and the problem is still going to exist. People with the same problem have replaced far more to get no where. We've had 3 different mechanics come look at it to no avail. The computer says nothing is wrong - no codes at all. Out of all the threads of "fuel problem" has anyone actually fixed the problem?
My symptoms exactly mirror: http://www.automotiveforums.com/vbulletin/showthread.php?t=212039 .
I'm beginning to believe that no one has an answer. What we have troubleshooted is that in the throttle body there is injector A and injector B as well as plug A(for the injector) and plug B. When watching the injectors while cranking the motor injector A squirts and injector B sort of drips. Obviously we replaced injector B. No difference. So what we did was take plug A and plug it into injector B. Lo and behold, now injector B squirts gas and injector A drips. We have traced and retraced all the wires for wear and tear. Again, this all started VERY soon after being low on gas which is what makes us want to believe it is the fuel pump and I burnt it out or something. We've checked it 3 times and everytime the key is turned on (not started) the pump kicks on and fuel begins to flow. PLEASE... if you have any suggestions I would much appreciate it. I have read every thread on this subject so far as well as other research and have came to the conclusion that until someone can say "THIS is your problem" I am not pouring any more money into this piece of S#$%!! Thanks for your help.

UPDATE: Today I tried unhooking the MAP sensor and it tried to run a little better. Going to replace it tomorrow.

OK the pump flows fuel. But does it generate the required amount of fuel pressure? Since you are a TBI engine you should see 9-13psi when you turn on the key and the pump runs. If not, then you have either a weak fuel pump or a bad fuel pressure regulator. Since you ran it low on fuel, I'd guess you picked up a bunch of crap in the pickup strainer, in the tank, and that's holdin back your fuel... not allowing the pump to generate enough pressure. Just my $.02.