Good job testing!

Now you may want to test something that was mentioned by Jeremiah:
""At 4200 ft above sea level I usually start out with .075 or .080 IAB's in the Quickfuel stuff.""

Your IAB's will affect the A/F ratio way up into after the main circuit is starting in. If you have some larger IAB's or you have some drill bits, I would test the above statement. You could just put some larger IAB's up on the Primary side for testing if you only want to drill out a pair. Then if it works, then drill out a second pair for the secondary side.
I would suggest leaving in the .030 IFR's and start testing with the larger IAB's. If it starts good, and it gets rid of the glowing headers, then you are doing the same as if you were swapping in smaller IFRS. As long as your metering screws don't get too far out with the larger IAB's, you should be fine.

It would still be a good idea to buy the .036/.039ish sizes of MAB's for your testing too. You could also test with some smaller main jets than your current 64's since you found removing the MAB's leaned out the issue.

Nice job! You have put in allot of effort to try and figure this out. Some people would have just bought another carb instead of blaming their own lack of effort. Since you are at a much higher altitude than most, you have a little extra hurdle to jump.
I just hope you are keeping good notes! You will be flying through this tuning crapt once you get your wideband kit one day.