I also modded my Traeger with a Auberins PID controller. It took a little time to dial in the numbers with some help from the guys at the pelletheads forum but once I got them right it is perfection.
The PID thermocouple is placed at the center of the grill...
To start the grill you turn it on and set the temp. The PID will start the igniter rod automatically when the temp is below 150F(for starting and restarting if there is a flameout). Then turn the auger switch on for 30 seconds to add pellets to the chamber and then turn off. Once you see smoke you turn the auger switch back on and close the lid. Upper temp on display is the current temp and lower is the set temp.
At temp after 12 minutes...
I get very tight and accurate temps now. And a consistent light blue smoke. I can keep temps from 150F all the way to over 500F. If you own a Traeger this mod is a must