whats the mileage on the truck?
things to watch for.....
oooh, i just thought of something...i have replaced quite a few turbos on the new trucks....check your turbo whel for any excessive play. you could have a bad seal in the turbo, that only leaks over night...dripping just enough oil into the turbo to cause it to smoke. thats one scenario thats very possible.
otherwise, keep a close eye on the oil...if it starts to smell of fuel, you have a injector or ring problem. the biggest problem with cummins is they are loud...so, listening for "odd" noises such as spark knock from too much fuel or washed rings is useless. i would keep an eye on the oil, check the turbo for any signs of oil internally...other than that..run the hell out of it, if its still under warranty, let er eat.