I live in Golden CO and run at Bandimere speedway aprox 5800'.
I ran 13.56 w 65mm pulley and EC tune last April ....then went 13.3 with better off line in May.
I had problems with the Pirelli's hooking up. I have now got Nitto's on and they seem Much better so will see this coming April 24th if the feel is as good at the track. Thin air will definitely make you think the car is slower but so is everything else (other cars). I also have the installed 62mm pulley and new tune so we will see.