It’s not perfect math, the gap between someone living at 8000‘ and someone living at sea level, both riding at 8000‘ isn’t much (84% vs 88%).
So since you are better acclimatized than „not-acclimatized“ but not fully acclimatized to 8000‘, your power should be somewhat in the middle of the two values (86% give or take).
Regardless of that, while the occasional ride up to even higher elevation is great, I really would refrain from training at high altitude. Train as low as you can for best results. More watts are worth more than less watts to your progress (not only altitude, but also heat training or indoor training can have similar negative effect on having to train at a lower power). All of the above create a sub-optimal climate for performance gain.