Missing on the 6,8 I have done everything. Please help

[fire120ball]

So I have had a terrible misfire on the sixth and the eighth cylinder. It was worse before I did all of this stuff but its still bad enough. I have replaced the wires, the cap, rotor, points, I have replaced the condensor twice, Re-gapped the plugs (Plugs have under 10K on em), hit the plugs with some sand paper to clean them up. I checked if it has spark... It does, and then today I went to check out how the spark was.. And it was yellow, Which I know its supposed to be blue, and I THOUGHT it was a valve or needed to be relashed, now that I see the voltage is not good. What should I do!?!!?? replace the Distributor? all of the other cylinders seem fine. when I pull the plugs,. Please any help would be awesome!