First off this truck has alot of history for sake of keeping this short im going to leave that out.

This is a 99 4.3L x code engine. About a year ago I had the fuel pump and left side head gasket replaced.Emideately after that the problems started.Between 1800 and 2500 rpm the engine surges and almostacts like it dose not want to change gears. At start up it smells very richand sometimes shuts off. We have ran the codes multiple times and it always brings up a code for the secondary fuel system. Which when reset truck runs GREAT for about 10 min. Then reverts back to the problem. If anyone has heard of this or has an idea what could fixthis please post. Im at the end of my rope with this,and have contemplated selling the truck.

Parts changed
Fuel pump
distributor cap (cracked)
plugs
wires

hello jdodno, i would try resetting the pcm by disconecting the battery for about thirty minits, if that dose not help my next thought would be a worntimeing chaincausing it to throw your code and making the pcm over conpensate-running rich-i have the same motor and year, and the pcm will affectthe transmissiom to a degree. when the timeing chain starts wearing there is no coad for time to replace me.
so check your timeing. hope this helps .

do you know the exact code?..sounds like an internal fuel leak

Thanks for the replys. I wish I could give the codes that the computer is kicking out but im over 9000 miles away from the truck. In about two weeks im having the truck towed to a shop and they are going to attempt to go through the engine and replace broke or worn sensors to try to fix the prob. Thanks again. Ill post the fix on here when I know what is was.