I just bought a 2006 f150 with 39000 miles. I love it. I heard nothing but good things about the 4.2 engine. The only problem is I have a rough idle while in park. I heard a lot of people say "it's just the nature of the 4.2." Is this normal? I replaced the fuel filter and disconnected the battery to relearn info and still it idles rough in park. What the hell is wrong?