DC: I couldn't find that discussion but are you referring to TSB 08-008-04 (Copper RE16MC plugs)? It mentions that they are more resistant to "cold engine carbon fouling". I can use my current ignition wires, right? They were replaced 2 years ago when I installed the E3 Premium #E3.66 plugs. Are the Champion Copper Plus plugs gapped properly right out of the box? I have never gapped a plug before nor do I use a torque tester. I have always tightened by hand until they don't turn anymore.

UPDATE: I just popped in a set of CHAMPION COPPER PLUS Spark Plugs (#443) and am about to embark on a 20 mile round trip at 70 MPH. I noticed immediately that she idles better than ever. The E3 Premium #E3.66 plugs I removed were a mess. One was even loose and covered in oil (cylinder closest to driver side). Hope that didn't cause any permanent engine damage ...

Oil fouling may be a symptom of leaking valve seals. Not good. If it was loose, maybe the oil came from outside. Any oil up top?