Welcome aboard, Tasty! Is this your first smoke in your SI? We have folks in your neck of the woods who don't have a problem. Unless you are monitoring the box temp constantly, you may be seeing it on the low side of the temp swing (it will do that). The altitude may play a factor, but maybe our other CO folks will chime in on that. I'd just leave it on max, and watch internal temp. It may take longer, but it will get done. Merry Christmas!