Agreed. So much impacts power output too. Hydration, heat, elevation, position on the saddle (climbing vs. aero position), and even the flywheel effect (little ring vs. big ring, and your trainer model). The search for a static FTP within a narrow margin of error doesn't seem to be worthwhile given this. All of these tests have a huge psychological component too so even simply having the wrong mood can impact your numbers. Focusing on a consistent measure and using that as a guide for training is the best you can hope for. Congrats on your gains OP! I was able to put +94w on my FTP over 2 years using ramp tests. Keep it up!