I have an 05 SC King Ranch 4x4. A couple of months ago it missed a couple of times and I got a CEL. I pulled the code a PO308 #8 misfire. It cleared and recently came back. I swapped the COP from 4 to 8 to see if the problem would move. It did. I purchased a new COP from NAPA. No Fix. I tested the plug. Good. When you drive the truck it runs fine at 2k 65mph. Hammer down it starts missing till you back off. You can pull the injector plug off and it doesn't affect the engine at all idling. Could it be the injector? Any thoughts? BTW when I bought the truck. The previous owner transfered the Fidelity Warranty extended warranty to me Plantinum coverage. Has anyone dealt with this company?

 

if it has a warranty, use it! if not, replace that injector

 

FWIW, I took it in. #5 injector failure and both O2 sensors were bad. All fixed under warranty. I'm not as dumb as I thought I was