I have a set of 245/75/16 tires I use solely for my track set up. I have never seen anyone else running them, are they too small? I have a set of 285/75/16 too but they are mud tires and are triple the weight.
What kind of boost levels were you seeing when it started to surge? Mine surged then would die off, threw some of the same codes including the EGR ones.
Im having the same issues with mine right now. I sent a log to my tuner to look at but I think it may be non tune related. Im going to mess with it this week.
Keep us posted.