I did this exact same thing on a 94 factory turbo f350. The guy had to have the pump rebuilt because of a leak, and while it was in the shop, the rebuilder "turned it up" a unkown amount. It smoked when you got on it hard pretty bad, which didn't bother the guy who had it, but he felt is fuel mileage was suffering.
So I got the truck and turned it down 2 flats. I then tested it, and the smoke was gone, and it was noticeably down on power, but he wanted to try it. He hauls a boat down to the eastern shore every year, and after I turned it down 2 flats, he said he was losing speed going up the east side of Afton mountain on I-64 coming home hauling the boat(he sets the cruise control). So I went back in and turned it back up one flat, and it was perfect, just a little bit of smoke, and plenty of power going up the mountain. I felt like he might have gained a little bit in fuel mileage, but I am not sure he really did. I do know afterward when going home from work, he would have good heat out of the heater in about 2 miles. After I turned it down, he doesn't get any heat out of the heater till about 5 miles down the road.
I wouldn't turn it 2 turns. I would be very conservative, the adjustment is touchy. When you read "turned it one flat" that is one flat on the allen wrench. The allen wrench has 6 sides, so that is only 1/6 of a turn.