one spark plug looks burnt.
 

what would cause number 6 spark plug to look burned on the outside.?

Mybe spark arcing from cable cap to engine.

thats what I was thinking

put up a picture.

desirably of the whole engine set.

i bet i can tell you exactly what is occurring.

First question I always ask:

a) What kind of Spark Plugs?

b) Resistor? Non-Resistor?

c) Pictures would be AWESOME.

can't put up photos since they changed the way of uploading.All five Denso 5061 plugs look normal.Just number 6 looks burnt.Brownisk look from metal base to a little bit of the ceramic portion.I think it might have been (the wire arching).Will use conductive grease instead of dielectric
I always run Denso 5061 because i SOMETIMES RUN NITROUS.

Denso 5061 = multi ground electrodes and resistor type...
Not the best selection if you want to make power with reliability.

"Grease" not really necessary if you have good boots/contact terminals on your wires.
Grease can become contaminated which can cause tracking from the spark plug tip in the boot to ground.

I've noticed all the problems you've posted since you've been using nitrous.
Coincidence or cause ?

I have not used nitrous in over a year.These are plugs less than 4 months old.Maybe I just got a bad plug? I will switch back to NGK

The engine management is very sensitive to the correct non-resistor type spark plugs.....
Hi-tech plugs tend to have a smaller diameter electrode made of semi-precious metal.

The M103 and M104 prefer a larger diameter solid copper or silver electrode in a non-resistor design.

Ed A.