I'm currently in Durango, Colorado. I left Durango a few days ago and was in Moab, then just got back to Durango. At higher altitude, the Toyota runs like complete 
. 2nd gear 15/20mph up mountain passes and it now has a weird sound as though there's an exhaust leak, kind of a buzzing noise as I'm on the throttle. Oh, and the loss of power is a joke. I don't have any jets to re-jet. So I may mess with the idle a bit. Once I'm back home though, I'm saving up for a 3rz to put in it. The 20r was just recently rebuilt, bored .20. Maybe it's time to retire it..
Also, while going up hills, there's a strong smell of gas. I assume it's running really rich at these altitudes, that won't hurt it, right?
I don't remember having that much of a power loss on the passes in the Durango area, but I did have to drive it like a racecar to keep my momentum. It's been long enough that I can't remember if I was trying to maintain momentum in 3rd gear or 4th, but knowing that I could run 60+ mph in 3rd I double I was going fast enough to warrant 4th gear.
I do distinctly remember dropping into 2nd gear on the eastbound side of Vail Pass and also the Eisenhower tunnel approach. Elevation is no joke, significant power loss is to be expected.
Snoqualmie Pass here in Washington is a joke compared to the mountains of Colorado. In my 85 I could maintain 70+ mph in 4th all the way to the top if I was able to keep it rolling. The 4Runner is heavy enough that I have to drop into 3rd no matter what for a couple of sections.
My Weber was run exactly like it came out of the box and I lived in Colorado Springs at the time. If your Weber has been tuned for Texas it's possible that it's a much bigger change going to high elevation.
