1996 Chevy Silverado hard to start, no power

Hey Guy, i have a problem! My 96 Silverado is very hard to start once it has been sitting! I already put new plugs, new feul filter, new plug wire, new cap and rotor kit, new air filter and it still hard to crank! I have already checked the feul pump pressure and its good! I have to end up putting a little gas in the throttle body for it to start right up! And once it starts, it has no power if you put the pedal to the floor! Wats the problem?