This may sound stupid...but have you checked the tempererature range of your plug?
I know on 2 strokes it makes a big difference (like stalling a 400 scrambler in snow when the engine was hot -imagine...a scrambler 4x4 being towed in half foot of fresh powder snow by a banshee...there has been quite some pushing action...ahahah). Even though the Raptor is a thumper...maybe the hot AZ weather pushes your plug to its limits and beyond...Worth a try anyways...

Tell us when you find out!!!

 

Guys, read my new post "Update on the Raptor problem from hell" for a continuation on this, and to learn about my progress. (Or better said, lack-thereof!) Thanks.