I don't smoke loin. It's too lean. I'd roast it at 350 - 375 over wood coals with an internal probe. Take it to 140 and let it rest for 15 minutes.
Spot on advice. Pork loin is one of the best tasting meat cuts when cooked properly and one of the worst when overcooked. If you don't have a good internal thermometer, get one now and learn to use it. You will be like me and discover your meat cooking skills will raise dramatically when you quit overcooking most meats.