Hi all I have a 2011 f150 ecoboost with 17654 miles tonight I noticed when on the highway going about 65mph I had to accelerate and I noticed a large puff of smoke from the rear of truck. I accelerated again and another puff of smoke again. I was following my wife so I called her and told her I was going to pull ahead of her and for her to look for smoke while I accelerated. I accelerated 3 times in front of her and no smoke, it was night time so I could not tell what color it was. Wondering if anyone has any ideas.