I tore into my 02 durango with the 4.7 trying to resolve a ticking issue and as I tore it down I found that the #4&6 cylinder spark plugs are completely corroded from the threads up to about half way up the porcelain, the plug boots and the bottom of those two cylinders is also covered in what appears to be rusty water, looking into the hole I don't see any moisture, what the hell is going on?