As posted in the MD comparison thread:
I'm trying to glean a little knowledge from that thread. Can someone, David maybe, tell me how you go about checking for this "arching"? My stock plug wires have about 95K miles on them. I have a replacement set sitting on my bench, but I'd like to check for arcing before I install them. Will the arching show up during idle or does the car need to be on a dyno to see it?

Yes... I did a search before posting this.

 

When David pulled off the plug wire cover he pointed the the inside wall of the valve cover and wiped off some black sooty dust with his finger and said "yup, it's arching".

He also said that 30k miles is too many for the wires so 9o+k miles seems to make me think you may be ready.

 

Ah, so it was evidence of arcing and not arcing itself that was seen. I guess I'll go ahead and replace them. Do the wires/extensions under the coils need to be replaced as well?