Happens after setting
Truck is completely stock 6.0L 2004 F-250, owned since day one. After setting for atleast over night, when I start it up and and drive out of my drive way to the main road (a block) it runs fine, (under 2,000 Rpm). As soon as I hit the pavement and get up to speed and hit 2,000 Rpm's, it acts as if I have a Rev Limiter set and it blows greyish/whitish smoke. After driving for 4 miles under 2,000 Rpm's is clears up and run's normal. I can go everywhere all day and start it back up after setting for 2, 3, or more hours and runs normal. It happens after setting just over night (8 or so hours). No check engine light. Any ideas???