I would assume PEI would stand for Prince Edwards Island???
I would speculate your 33 mpg in hills could have some other factors involved like strong head wind, climbing most of the time or high speed driving. I also think keeping exact speed regardless if going up or down would waste more fuel, I usually speed up down the hill and let the car bleed some of that speed towards top, (of course traffic permitting, but most cars, especially heavier trucks would drive like that by nature any way), but it's always nice to have some momentum build up going up the hill. As a matter of fact I always get my best MPG on winding hills, like Blue Ridge Parkway. My own theory is that regardless of the hills, the biggest mpg enemy is my fast 75-85 miles per hour driving and being forced to drive at much lower speeds in the mountains keeps my MPG up, even if the hills make it less efficient.