1989 s-10 blazer 4x4

i have a 4.3 engine that ran good, but all of a sudden when its cold it is hard to start, the inside of the rotor is black with carbon and it will start if you dont touch the gas but you cant step on it untill it warms up, i replaced the the cap and rotor and the dist module,spark module, computor,ect, i recently replaced the fuel tank and pump so now im going to check for fuel presure, any ideas?