My latest Gen 2 has NGK ZFR6FGP spark plugs in it which are heat range 6 which is counter intuitive to everything I've read. Stock heat range is 4 and alot of guys drop down to a colder range 3 plug to alleviate pinging. The truck runs decent but had some pinging that I figured the plenum gasket was causing. My question is under what circumstance would you use that hot of a plug? Thanks. Almost forgot It's a 5.9 Magnum. Edit: Never mind I just figured out there is no set industry standard for spark plug heat range and almost all brands have a totally different numerical grading system . My bad.