I had an issue on stock turbo with the car wanting to overheat on passes. It doesn't help the unbearable heat that we have here in Idaho at times though. I was on a e30 tune by Randy @ Mountune. The car did pretty good, but if I was putting too much load on the car going up a pass, my coolant temps would climb out of control. My charge temps always looked fine. Haven't had the issues on the GTX2867r though....