92 S15 runs rough when low on gas

I have an odd problem. When my tank gets below 1/4, the truck runs rough and will sometimes die. I tried putting in premium gas, and some water remover, didn't fix things. I replaced the fuel filter and this didn't help either. When the tank is full, it runs well enough although I occasionally hear a squeaking noise (a short sucking sound) coming from the area of the tank, and the engine misses when I hear this. I had the fuel pressure checked when the tank was full, the GMC mechanic said the pressure was OK but suggested that the pump might be getting weak and not working right when the impeller wasn't completely submerged. Does anyone have an opinion on whether this is likely, or maybe is there another explanation? Is it possible that the strainer in the tank is clogged at the bottom? Does the fuel pump sit in the tank vertically? I would like to do the repair myself if possible. I understand you have to drop the tank to get to the fuel pump. Do I need to siphon the gas out first? Will this job be dnagerous to do in a garage with a gas water heater? Any advice on that would also be appreciated. Thanks in advance.

By the way, this little truck has been pretty good for me. It has 116K miles, and I've only ever had to replace the heater core (2X) and the parking brake lever. The power window won't work on my side, haven't tackled that one yet but it would be nice to hang my arm out of the window again! And the brake cylinder seems to be leaking, but I just keep adding fluid for now. Oh yeah the smog pump seized and broke the serp belt, I got one that bypasses the pump. And I replaced the alternator recently. Hey, come to think of it this thing is a piece of junk! Just kidding. Every month without a payment is a good month.

I chickened/lazied out on replacing the pump myself. My mechanic is putting it on for $115 plus the pump. I talked to him this morning and he was skeptical about the problem being the pump but said he would check it out. Called back at noon and he said the pump WAS bad, the pressure was way down from what it should be (I think he said 12psi) . I guess it was due to the tank being half full as opposed to full (when the GMC mechanic checked the pressure and said it was alright).

Anyway, thats the report. Hope this fix does the trick, and I hope someone else can benefit from this thread. This is a useful forum, I got some good tips reading through here.