Fuel starvation?

I have a 1988 S10 pickup, 2wd, approx 160k miles, 4cyl. The truck has never given any problems in the past few years, then the other day as I was headed to work, I was on empty, so I stopped and filled the tank with gas, and as I continued on my way to work about 5 miles down the road the engine stumbled and stalled and I was unable to restart it. I called for a lift the rest of the way to work and decided to check it out after work. Long story short, I wound up towing the truck home. I have replaced the fuel filter and ignition module (the fuel pump was replaced a few years ago). I thought the fuel pump might be bad, so I disconnected the fuel line after the filter, connected a hose to it, and ran the other end into a gas can. I used the relay bypass to energize the pump, and proceeded to pump out the gas. The fuel pump is working. What I am wondering, though, is, can the pump still be working but not delivering enough gas to the engine? I re-installed the fuel filter and poured about a tablespoon of gas into the TBI and the engine started but ran real poorly, surging, and finally stalled again. Should I drain the tank and replace the pump, or look somewhere else first? Thanks.