I have a 2001 SuperCrew 4.6L with only 79,000 miles that has started smoking on start up. It started after it sat for a few days and on start up it ran really rough and was smoking baddly. Now if it sits just a day it will smoke on start up but runs fine. I let it set several days but the rough running didn't come back but it did smoke. Also seems worse if it is parked uphill. Is this just valve guides leaking or could it be a cracked head gasket? It isn't using any oil between changes and I change it every 2500-3000 miles because I tow a bassboat with it alot. Has anyone else had this problem? I'd like to get some information before taking it to the dealer because I have the 100,000 mile warranty and want to get it fixed before that runs out. Thanks for any and all help.