Last night I tried a variation of the 2-2-1 recipe for baby backs in my medium Big Green Egg and they came out fantastically well. I can attest that there were no leftovers! I use 250º for my cook monitored by a BBQ Guru DigiQ. After 2 hours on the grate I wrapped my ribs in heavy duty aluminum foil, and sprinkled them liberally with dark brown sugar and topped that off with margarine before I closed them up and returned them to the BGE for another hour. (I use Parkay from a squeeze bottle for ease of application.) After one hour (not two) I unwrap them and put them back in the BGE, unwrapped, for another hour. I coat them with BBQ sauce 20-30 minutes before they come off.
The extra 25º is what I think shortens the cooking time for the middle step from 2 hours to 1. I find that if the ribs stay in foil too long, all of the rub is washed off by the steam. The ribs may be tender, but they also lose flavor. My "secret" to avoid that is to use a rub and let the ribs sit in plastic wrap overnight. That allows all of the spices to seep into the meat and add flavor that isn't just sprinkled on top.
You might think that these ribs would be too sweet, but the margarine and sugar quickly melt together and steam the sweetness into the meat. Combined with a good rub, the combination is delicious. I've also seen on Pitmasters where cooks use a combination of dark brown sugar and honey, along with the margarine, but since this was my first time trying this method, I was a bit shy about they're coming out too sweet.