FTP Testing at Higher Elevations

I have a question about FTP tests at elevation. I’ve recently moved to about 6,800’ from about 500’ and while I was expecting the related decline in FTP, even after acclimatizing (see https://www.trainingpeaks.com/blog/the-effect-of-racing-at-altitude/ which would suggest I should be at ~91% vs. sea level), I feel like something else is going on. When I used to test at the lower elevation, I would sometimes have days where my lungs would give out first and sometimes reached the end due to leg fatigue, but neither ever felt far behind the other. Now when testing at elevation, it’s always my legs that give out first, and always way before I feel like my lungs would give out. Also my HR is much lower when my legs fatigue. My max HR in 2 tests at higher elevation have been 176 and 178, whereas in the last few tests at the lower elevation I maxed out at 190 and 184. It’s a very obvious difference in terms of how my legs start to hurt late in the test, causing me to quit before I feel like I should be ready. What’s happening? Anyone else experience this? Is it something that can be overcome?

One more point of reference, a few outside rides since my most recent test have had very high intensity factors despite me not feeling like I went that hard. For example this morning a 54 minute ride had an IF of .96, and while I was pushing there was definitely more to be had.