fuel pump or no?

I've read all the fuel pump and stalling issues on this thread, as well as about 1/2 the internet. They're all close, but not quite what I'm dealing with. I've got a 1988 Chevy K1500, shortly after I bought it, it would occasionally stall upon accelleration (during highway driving), after running for about 20 to 30 miles or so. The truck didn't mind if I put it in neutral, cranked the starter, back to drive, and kept going. A couple months later, it started getting worse, all of a sudden. During city driving, it started stalling at every stoplight, AND on accelleration. Now, it's finally gotten so bad, that the truck will ONLY run, if it's on level ground. If I am on even a slight incline, the truck will stall. It seems to run fine "under load" though, but again, only on level ground. If I try to go uphill at all, it suddenly acts like it is getting no fuel, and chokes out. I can rarely recover it by pumping the gas pedal like mad, though I get the feeling that's like taking a sugar pill. I have also noticed, that the problem gets worse, the less gas there is in the tank. I am about to begin the wonderful procedure of dropping the tank and replacing the pump, though I'm nervous to do so, if that is NOT the problem... (tight budget).

Any suggestions would be great- oh, and all the forums say there should be 3 wires going to the pump... but with my hands over the top, I can count 4?

I had the same problem with my truck recently.. ended up being the fuel filter.. Have you tried changing that?

That seems to have been the problem... Thanks for the tip there, $5 filter vs. $30 pump... :) My SE Light keeps coming on still though, and today, the truck tried ONCE to lug then surge.. I dumped some HEET (anti-water) and injector cleaner into it with some fresh gas, and that seems to have helped there. I'm fairly sure my SE light is related to the knock sensor, but... can the knock sensor going bad cause similar problems to the filter/pump being dead?

No, the knock sensor has nothing to do with the pump, it has to do with timing.