looked up Denver, it's 5200'
I'll guess you will notice quite a difference at 8000'. Folks have reported trouble cracking 200ºF that high up when using water.
Try a waterless cook, using sand, an inverted clay pot saucer or crumpled foil balls. This will provide a shield from direct heat without the heat sink properties of water. Whichever you try cover it with tinfoil, this you can change the top foil after each cook to make clean up easy.
If you usually use water try a little less lit to start with and your vents will likely end up being open less than usual.
Your temps will move around a bit more than with water but it's not a problem.