Checking plugs for rich/lean conditions or "Reading plugs" on a vehicle running closed loop is a waste because, to accurately "read a plug" the truck has to be shut down immediately after a WOT run without allowing the PCM to go back to closed loop or even idle. It also takes a far bit of drive to color a plug.
A plug that has been ran under stoichiometric conditions will look as a lean condition. So the only way I can see to read a plug is to command the same a/f ration all the time Ie. 12.5:1 under all conditions... A better modernized option is a wide band.

 

Thats normal for the 6.2's.they tend to like less timing then cathedral port heads.Hope your tuner realizes that.You should also change the thermostat and fan setting as they run too hot imo.One good thing is if you get that tune down they run like a raped ape.I did some tuning on a 09 i believe.Ran a 15.0@92 in the beganing when i was done it went 14.4@99 with a little traction problem

 

Hope its fixed buddy!