While pulling my 10k trailer up a steep incline with the tow haul on, it down shifted a gear and reved to about 2700rpm. The truck held the rpm for a bit but soon started to shutter or jerk four or five quick times. I looked at the tack while it was doing this and the rpm was still 2700. After it did this it seemed like it had very little power. It only has done this three times but in the exact same situation. The dealer thinks it is my egr, but I just replaced that 25000kms ago. Any ideas of what it could be?:help Ps My truck is 100% stock!