I have a 98 astro and am having an accleration issue - runs fine if you dont have to "stomp" on the acclerator - if you do have to step down hard from a dead stop it stumbles and hesistates - runs smooth if you just take of normal and dont get on it. Have changed the plugs. a

check coil, wires, cap & Rotor

try spraying water on stuff with a spray bottle and watch for sparks ro engine stumbling