Distributor bushings are known to wear and cause problems... remove the cap and check if you can move the rotor side to side, (radial play) if so, replace the distributor. As far as secondary ignition parts, (distributor cap, rotor, plug wires, plugs and ignition coil) you get what you pay for, just because it's new, is NO guarantee that it's good and it will perform properly. Secondary ignition is not the place to cut corners trying to save a couple of bucks. These 4.3L engines perform best when using AC Delco, stay away from aftermarket house brands, (Master Pro, Duralast, BWD, etc). Make sure the spark plugs are AC Delco 41-993 with a gap of .060 VERY important! AC Delco distributor cap D328A and put a dab of silicone dielectric grease on all terminals inside and out. Post your results.