GMC Truck Engine Runs Rough

I Have A 1994 Gmc 1500 With A 4.3l V6 It Started Running Crappy The Other Day And In Messing With It I Have Found That It Only Runs Fine In...

1990 Gmc 350 5.7 It Runs Rough At Low Rpms In Gear In Park Or Neutral It Runs Fine And Smooth But When I First Put It In Gear It Sputters...