What were your max rpm’s on both days and did you run the same gear ratio? You can tune with plug temps, but the main jet will get more results. Hotter plug on cold days and a cool plug on a hot day. Check your power valve blade for smooth operation.
I’m not sure on the RPM’s the only sensor I had was temp. I’ll have RPM sensor next race in a week. What brand plug does the rotax engine like? I plan on having a wide jet range to adjust, Plugs and gears