misfire cyl 6

i have a 96 blazer 4.3l. for the past year my truck would be hard to start if i let it sit for more than a day. after cranking for 30 secs it would start. a few days ago it wouldn't start. after sitting for a few hours it started, but it was misfiring and the the check engine light was flashing. i checked the code and found that it was a misfire on cyl 6 P0600. i checked for spark with a spark tester and spark was ok. i pulled the plug and the electrode was missing from the plug. i thought that was the problem but it still misfires after replacing the plup. i swaped the wire from cyl 4 to cyl 6 and the misfire didn't change. i also removed the cap and inpected the rotor it seemed to be ok. does anyone have any ideas i do have a cat that is rattleing could that be the problem

P0600 is a serial communication link malfunction. P0306 is misfire on cylinder #6. Which DTC was in memory?

sorry it was P0306

Swapping plug wires from one cylinder to another is not 100% conclusive. If a wire is faulty, it will still miss, just on a different cylinder. If your P0306 changes to a P0304, the wire is most likely the cause. If the P0306 remains, the wires are probably OK and the problem is elsewhere.

How long, (how many miles) has it been since it was tuned up and the fuel pressure was checked?

Good quality parts , (the kind you can't find at Autozone etc), are necessary. AC Delco spark plugs, distributor cap, rotor, plug wires and fuel filter.

Key on, engine off, fuel pump running, pressure must be 60psi to 66psi. After 2 to 3 seconds, the fuel pump will shut off and pressure must remain above 55psi for 3 to 5 minutes. Post your results.

i checked the fuel pressure today and it was at 60 with engine off and 55 while running after i shut it off i let it sit for 10 min and the pressure was at 55. i just replaced the plugs and the cap and rotor were replaced at 130000 and it has 166000 on it now. im not sure when i did the wires but when i swapped them the same code came right back. do you think it could be the fuel injector nozzle or should i try the cap and rotor first

Fuel pressure and leakdown are OK. If the same DTC came back, try the cap and rotor first. If the cap and rotor are not AC Delco, replace them with AC Delco parts. If it still gives P0306, there may be a problem with an injector, a vacuum leak, or any one of a host of other things. Just take one step at a time. What brand of plugs and wires are you using?