I ran 104's at someones suggestion I think early last year or something. They are definitely too cold for the average Wbody owner. Mine had serious signs of too much fuel and the scans at the track supported that.
I went to 605's and havent had that problem
Lee is right that is good info, helps save a little money overall to buy cheaper plugs.
Steven Oliver
2004 GTP comp-g WS6. Gator and suede all around interior.
Advanced MECP certified installer, custom upholsterer.