I have been having a very similar problem with a 96 Gulf Stream. 460 Engine. After running just fine down the highway for 45 minutes or so it will begin acting like a vapor lock when accelerating into a hill, Losing power etc. It never actually dies. When I pull over it will still Idle. If I shut off the engine even for a few seconds, I can go again for a short ways. The longer I drive, the more frequently this happens.
My mechanic is mystified, as the fuel pressure is good. All his diagnostics say fuel pump is fine, but he never got it to act up.
Sounds like I am experiencing the weak/dying fuel pump issue?
