1999 sonoma lugging [cutting out]

I have a 1999 gmc sonoma v6 it runs good when it is pullin but when it is coasting it feels like the engine is cutting out [lugs]
I have changed plugs,wires,cap.rotor and fuel filter.. But I still get a random error code [P0300] for engine misfires

P0300 is usually caused by secondary ignition. Did you use silicone dielectric on both ends of the plug wires and coil wire, and also on the terminals inside the distributor cap?