Engine misfire?

Had a misfire replace 1plug & 1coil. Still runnin rough. Any other ideas

Cylinders 1-3-5-7 are on the drivers side. First I checked for continuity between the primary and secondary circuts on all ciols and found 0.0 omhs. Then I found constant 13.5 v on the negitive side by putting red lead of volt meter to positive power. On positive side of coil connecter I got a intermitent reading from 5.2v-10.6v. Each coil has different colored wires. If the PCM did quit I don't think then truck would run at all. Would a comperesion test be in order to see if there is proper conditions for smooth idle?

Based off some other issues I am having. Like white exhaust in the morning & loss of coolant. (It's not leaking did a pressure test)
Could be the head gasket?

I have a 1998 durango with a 5.2L. It has a #1 Cylinder misfire and the Light is on with said code. I have done a tune up (plugs, wires, cap, rotor, air, fuel, pcv) and cleared the code. The light came back on during the second drive cycle. I pulled the injector rail off checked the fuel injectors by comparing fuel spray pattern and #1 looks no different than the others and injector has a normal pulse width. I then did a compresssion check and all cylinders including #1 were 150#- 160# on two complete test cycles. Except #8 cylinder was 90#-120#.
Could the low compression in #8 be causing a #1 cylinder misfire code in the ECM? Also when I accelerate the blower air goes from the dash vents to the floor vents and as soon as I let off the gas it returns to the dash vents? Could this also be related to the misfire code?
I have had a chevrolet truck in my shop that had a #3 misfire and it ended up being the downstream O2 sensor on bank two. Could my problem be a o2 sensor? I hate to just start changeing o2 sensors $$$$ any help would be awsome thanks.
ERIC

I have a 2000 Dodge Durango 5.9 4X4 about 50,000 miles on a dodge rebuilt engine, with a problem I cannot seem to isolate. Symptoms are: spark plug in cylinder 7 will foul after 2 months, the plug looks good, its the plugs threads which gets a build up of what looks like a caramelized gas mixture and this goes all the way to the plugs compression ring with some of the material on the compression ring. I have replaced dist. Cap and rotor twice, plug wires twice, spark plugs 3 times, Champion Iridium. Compression test, high cylinders around 145 -150
with cylinders 5 & 7 being the lowest at 135. Test preformed 4 revolutions on each cylinder, all plugs out throttle closed. I have tried injector cleaner, no change. I have talked to several local mechanics locally who scratch their heads and say "never heard/saw that before" My fear is that there is a crack in the head at the threads, your thoughts. If you need a photo of the spark plugs, I can provide later today. Thanks in advance Mike Wywias