Here's a few of mine.
http://www.smokingmeatforums.com/t/169460/easy-smoked-pork-tenderloin-foamheart
I am pretty simple, I like my meat to taste like meat. I have tried brines, never attempted an injection. Injections are huge puddles of flavor and I never thought any of my tenderloins could dispensate that much consentrated juice.
I most like Ancho & cayenne pepper, and a very little garlic and onion. Wrap and rest two days. When you pull for the smoker, lightly rub down withd salt and at the very last minute a small coating of light brown sugar. The heat and the sugar compliment, while the suagr also will liquify, caramelize, then crystalize to help hold the juices.
The ancho is a very earth pepper taste which doesn't permeate to deep along with the cayenne. You will notice the second day how outstanding your refridgerator smells when you open it, seriously!
To me the tenderloin is more about the maintaining a low enough temp long enough to get good smoke without over cooking. Its the gentilest low & slow I ever do. You understand the 4/140 rule. You are trying to achieve that perfect pull temp just as it hits the limits abosorbing the max smoke it can.
Time temp and smoke absorption are the most important aspects of doing a tenderloin to me. It tastes like a pork tenderloin, perfectly cooked with a great pecan smoke (or whatever is your favorite), and the meat........ you need a spoon to eat it , its's so tender.
1. 4/140 rule, I know there is no bone and one pure muscle, work with me here.
2. Apply smoke a regulate anyway possible to achieve that pull temp at the 4 hour mark.
3. Everything else is just smoke and mirrors. Salt is really all you need.
Of course I could be wrong, there are so many great smokers here and each has their own way. But this is my way.