Those of you with a 2004-2008 5.4 Triton 3v engine, I have first hand experience on the spark plug epic! I bought the Lisle 65600 tool and tried the Champion replacements with horrible results. I had to buy the Autolites to make my Navigator run smoothly again. Reply if you need details or wish to have more detailed advice. I have had best results with a HOT engine, replace 4 plugs on one side, then heat the engine up again to change the other side. Despite what the attached TSB states HOT is the best way. http://www.dslreports.com/r0/download/1455834~b715e5c331a16b8f9799c2c716d9b7e4/Ford_TSB-0819.pdf