With many miles on the truck I would suggest changing to a set #140033-8 of Accel COPs. Summit has them for around $270 + handling fee for the set. I put the 7989 Champion plugs and the Accel COPs in mine @ 71,000 with no problems since. I have over 31k on them. I noticed you had an '05 which has had problems with the injectors sticking. You should check that out also. They usually flood a cylinder and can ruin the cats in some cases. If you change your plugs have a Lisle tool set on hand and follow the TSB. Let the plugs soak overnight if possible. I broke 7 when I changed mine. Patience is a must on this engines.