Here is what I have done for a large pork loin. I love mine smoked.
1. Make sure you get all the silver skin off before you start smoking.
2. I inject a mixture of maple syrup and creole seasoning into the loin to add moisture and flavor.
3. I smoke it (with apple wood if you have it) at 225-230 to a medium done internal temp of 155. No foil.
4. Once it hits 155 IT, pull it, wrap it in foil and a towel for about 30 minutes - then pull and slice.
I like my loin with some apple cinnamon sauce, which is very easy to do while the loin is smoking.
a. finely chop two large or three medium sweet apples (Fuji, Galas, golden delicious all work fine) and place them in a saucepan.
b. Add one table spoon sugar, 1/2 teaspoon each of cinnamon, paprika, salt & white pepper, and 2 tablespoons rice wine vinegar.
c. Cover and bring to a boil over medium heat then lower to a simmer. Cook slowly till the apples are tender.