[WRXlerate]

So, for those that are reading and don't know, the engine was out of an 07 sti that was swapped into my wagon. I am running a Mishimoto alum rad. Engine has 22k mi on it. Coolant level was good before and after. I could hear the cooling fans buzzing away after each run.
Issue: After each run at Auto X this last saturday, my water temp was way above normal (nearing the 2 o'clock position on the oem gauge). I have never had any overheating issues in any previous stis I've owned even after 10+minute hill climbs. The only thing I can think of is that I don't have the plastic undertray on the car. Would that cause it to overheat? Or do you have any other ideas because I'm stumped. I don't know how to check for air in the coolant passages but would imagine that could also cause this.
Any ideas would be appreciated.