greyish black smoke getting worse under normal acceleration. fuel milage getting worse. hwy mpg has gone from 14.5 to 11.8(hand calculated), over the past month. Truck is stock and still seems to run fine, any idea's what could cause this?

 

TAKE IT TO THE FORD DEALER

 

ITS REGENERATION, AND WILL OCCUR EVERY 60-120 MILES, AND YOU WILL GET HORRIBLE MPG'S DURING THE REGEN CYCLE- ITS GETTING BROKEN IN TOO - GET A SCT LIVEWIRE, DPF/CAT DELETE PIPE, AND DRIVE IT NORMAL, AND YOU WILL GET 20MPG - GET INNOVATIVE DIESEL TO WRITE YOU THEIR 350HP TUNE,AND YOU WILL GET 25MPG, AND BE RUNNING WITH 600HP !! ROLL SOME COAL