Great running truck. I've owned it for almost 5 years. 770k miles. It started with a egr engine light and code. Mechanic replaced egr. Code was cleared, truck seemed to run fine. Hauled some loads at night, no problems. Few days later, pulling heavy load in the afternoon, truck losses top end power, won't accelerate, but can maintain some level of power. No engine lights or codes. Limp it home, later that night it runs fine, get it to act up next day. Take mechanic on test drive, while hooked to diagnostic computer, it does it again, he says the intake goes from boost to vacuum at times. He thinks it's the throttle valve or the ecm. Goes to replace the throttle valve and finds oil in the intake. Says turbo is bad, replaced turbo, throttle valve. Truck seems to run fine, again at night, but sometimes during the day, it does the same thing. One other clue, air filter gauge, which had never shown a high vacuum is maxing out. Filter is coming for replacement. When truck is experiencing the problem if you press the throttle beyond the point of maintaining power you get black smoke from exhaust, but no additional power.