Replaced the plugs on my 03 4.7 today. And I noticed that all the plugs had corrosion on them (the nut part of the plug not the threads or the connector). Checked all of the O-rings on the coil packs looked good. Also it looks as if the o-rings have done a good job of keeping junk and crap outta there. The plugs look like that they could have been original, I cant beleive the truck ran as smooth as it did with those plugs in.Main question is, is it normal to have this or has anyone else seen this?? Thanks....