Attached is one photo looking down into the barrel of a spark plug where you can see some arcing where the spring from the spark plug connector touches.  The second photo shows the end of the spring and evidence of arcing from the spring to the plug.  Evidence of arcing shows up in the downloaded engine data as well.  Question is has anyone seen this before and what was the solution to correcting this problem?  Having followed the instructions below, I am at a loss.  There are three plugs, #2, #4 and  #6 bottom plugs only with this problem.  The Slick mag that is operating these plugs was overhauled in February of this year.  When I put in new springs and changed the plugs the problem went away for approximately 3 flight hours but now is back.

The key to successful installation of the
connector onto the spark plug is keeping
everything clean and dry.
• Handle terminal sleeves only with clean,
dry hands.
• Before installing the connector, wipe it
with a clean, lint-free cloth moistened in
methylethylketone, acetone, wood
alcohol or naphtha.
• Inspect all terminal assemblies and
replace those showing evidence of
mechanical or electrical failure. (If Dow
Corning Compound is to be used, see
next section now.)
• Make certain that the inside of the spark
shielding barrel is clean and dry.
• Without touching the connector or
spring with the fingers, insert the assembly
in a straight line with the spark plug.