Remove the serp belt completely - start the truck without belt - Try to locate it again or listen for any changes - Shut it down in about 5 minutes or so - let it cool , reinstall belt..

Post your findings

 

what is this????

loacted passenger side

 

what are some sure signs of a wrist pin knock?

 

I have the same exhaust system on my 2002 Supercrew and had a similar problem. You probably already checked this but if the exhaust is touching the frame, body, or bumper anywhere is can cause a vibration that will seem it is coming from the engine. Check to make sure nothing is rubbing and all clamps and rubber mounts are tight and in the correct place. Also make sure you reinstalled the balancer that is between the cat and the muffler. I put heavier duty clamps on my system than the ones that came with it and they hold a lot better without lossening. These are things that I checked and it fixed my system.