to me that sounds pretty close to what I am seeing on my wifes truck. She has a 2k1. 5 Auto, when I decided get off of my butt and install gauges on it, I replaced the stock airbox with a K&N RE-0880 and also replaced her stock peice of junk Hy-35 with my stock HX-35.
Max she can reach now is 1200 degrees.
So my honest advice is to do exactly what I did. Take that stock airbox off and trash it, then seeing that you have an auto, you should also have an HY-35 turbo on your truck. Call Piers and order one of his new tricked out HX-35's. It will not only lower your temps, but it will make your truck run a lot better.
Just my $. 02
Kev