2000 Chevy Truck

Ok let get some info here ok. Was the engine a new, reman, or salvage yard one? Did you replace the cap, rotor, plugs, wires and pcv valve? Did you clean the mass air flow unit (with mass air flow cleaner only)? How old is the fuel filter? Get back to me and we will go from there.

Brief history:
Original engine experienced bent valve in August - stopped using the truck then. Installed new factory GM long block 2 weeks ago. Rotor, cap, wires are new. Fuel filter was new in August when problem first developed and I thought that that could have been the problem. After new engine installed it idled nicely but seemed to lack power. Have since driven it approximately 250 miles - idle is rougher and seems like it lacks power. Tried to adjust distributor but get getting P1345 code until I rotated distributor slightly. As of now all codes are cleared. Friends say that distributor could be off one tooth but if all codes are clear can that be the case? Didn't fool around with any other sensors or apparatus ( prior to original engine going bad everything operated fine )

Ok I would change the fuel filter first as the vehicle sat for a few months and I would clean the mass air flow unit. Let me know how that goes.