Diesel Bombers - 94 6.5 turbo 2500 fuel issue

I've got a 94 6.5 chevy 2500, and it is frustrating the hell out of me. It died on me and started right back up, so I decided I should change the fuel filter. In doing that I found that the lift pump was not working. I replaced the OPS, and then the lift pump now they are working, but I'm still having the same problem. It will start and idle for about 15 minutes and then sound like it is not getting gas resulting in its death. Then it takes a few trys to get it going again if it starts at all. The next day it fires right up, and repeats this cycle. When trying to start it after it dies if I push down the gas it shakes like its still not getting fuel. When it does start it isn't blowing out any smoke or nothing just starts and you wouldn't even think there was a problem. Is there a pump on the gas tank, the guys at Shucks don't seem to think so, also they said it doesn't have any form of sock in the tank either. The fuel system just seems to lose pressure. It also isn't giving any codes. I'm at a loss and need help.