[tubman]

It could be a lot of things. If your fuel pump has a glass sediment bowl, carefully check the seal on it. I have found that this area is prone to air leaks that diminish the fuel supply. If unsure, it's probably best to replace the gasket. Surprisingly, I have had better luck with the old cork gaskets than the new neoprene ones. I once had to renew the sealing surface on the glass bowl itself using my surface plate (a large chunk of perfectly flat granite) and Wet-r-Dry sandpaper.