94 S10 loss's power

My 94 s10 seems to lose power when you give it full throttle, it dont seem like it is missing, i just put a new set of plugs in it 1week ago, when you punch the throttle it seems like it just sits there at the same speed, it has a 4.3 vortec throttle bodie engine automatic, the truck aint got but 84,000 miles on it, when I had changed the plugs, one of them was just plum full of black looking grease maybe carbon build up. When you crank it you have to give it a little gas it will fire right up and idle, it has no catalytic converter, the service engine light comes on but cuts back off, will it store any codes? If any one can point me to the problem I would greatly appriciate your help!