1998 S10 4.3 Vortec, 5 speed?

My truck has like a miss/jerking at cruising speed and light acceleration. It starts right up at any temp, idles fine, can rev it up in neutral no problems and works fine during harder acceleration while driving. At first I thought it was only when it was raining or damp but now happens always. I've replaced cap,rotor,wires,TPS,air and fuel filter...nothing helps. The only code I get is random misfire. i'm assuming it's not the fuel pump because it accelerates OK. Sure feels like something electrical. Don't know what else to check. Any ideas? Thanks.