hesitation

how about your plugs and wires? what grade fuel pump did ya use? Did you change the fuel pump sock also at the same time, and also did you change the filter when you changed the pump? If not that could have caused the pump to go out this soon, also check your fuel injectors, if it'll idel get so seafoam drop it in the tank and let her run for a couple hours, and top off your tank when she gets low to let the stuff take hold

Sounds like the catylitic converter might be stopped up.You might want to check the timing chain.