I just bought a '90 D250 5spd. 56,000 org. miles from the org. owner. This truck is stock. It blows blue-white smoke on heavy accels when cold but seems to go away when warmed up. I checked the valve stem seals-ok and blowby out the road draft tube-none. It seems to have consumed about a quart of oil in the 700 miles I've driven it. Should I pull the pipe and look at the turbo? Trans question - It seems to growl when I'm cruising or just maintaining my speed. Right at the transition point between accell and deaccelleration. Is that normal? Thanks, I appreciate any imput.