Pulled the head off and signs of definate detonation. Spark plug was blown apart and 1/2 of the electrode was gone. It left evidence of it's exit on the exhaust valve. Now it won't seat properly. Instead of fixing it, I ordered a set of Patriot stage III heads. Anyone want to buy a set of ported and polished 6.0 heads that need a valve job? Make offers!
Also still have my old 5.3 stock heads if anybody wants 'em for a reasonable offer.