Shifting/revving problem...need help.

Ok, I have a 98 GMC Z71 w/ a 350 vortec....it drives fine with no problems unless you "get on it"...then the rpms rev up but it won't hardly accelerate. However if I let off a little it will pick up speed. I noticed this on the interstate doing around 65-70 when I went to pass a car but it also does it in lower gears too(but only when I "get on it". Any suggestions as to what this could be? My friend's dad had his dually put in the shop today for the same thing and he was told it's something to do with his fuel pressure, is this possible? Any help is appreciated.

I've got the exact same problem on a 1993 GMC with the 350 vortec. The shop is exploring the problem now. Did you have any luck fixing the problem.

The shop exporing the same problem I've been having as yours, found that the engine had 75 pounds of oil pressure. They state that the oil pressure sensor commumicates with the fuel pump. If the oil pressure is too high, the fuel pump responds and cuts back on fuel pressure. They think the engine has clogged ports causing the pressure. The engine guys are pulling the engine out to replace it since they just put this new one in.