Not real sure what is going on here. I was coming back from BZN later afternoon as the sun was setting and my course was 270. Sunglasses were only marginal help and the haze up there was horrible. so, i nursed 00W up the 12500' to get over the haze. If i back the throttle out even 50RPM worth from WOT at that altitude there is no way to keep the EGT's below 1450. i know there isnt much wrong with running an 0-320 at WOT at 12,500 it just irritates me that I cant throttle back. WOT is about 2500RPM, back off to 2400 and EGT just starts rising, no matter how much or little, I lean it. go full throttle, it starts going back down. If i really lean aggressivly like i want to at that alt I get more RPM, but back the throttle out 1/4" EGT starts rising. As far as I can tell, there is no sweet spot except WOT and lean till rough then enrichen.