95 Sluggish

[fd2401]

My 95 was running good, developed a fuel leak, parked the truck for about 4 weeks, when i drove the truck again it was very sluggish until about 2600 rpm, (the fuel leak was the lift pump), the truck ran perfect when i parked it, when i got in it to take and have leak fixed it had no power. no codes, other than a code saying it has a chip (dont what kind). any ideas?
both valve cover gaskets replaced, did have one injector replaced that gave some problems every other time it was checked. Just confused has to why its down on power. the only thing i did was change the oil before i parked it,
rotella 15-40 added some lucas, the mechanic said the lucas was a poor idea,
drained it replaced with straight 15-40 delo, seemed to help it some but still not the truck it was before i parked it.

please help!