RPM drop 912UL

Hi folks,

I am relatively new to Rotax, but I did take the Rotax training few months ago and now trying to investigate a RPM drop on my engine. It is a 912UL, built in 2024 and has only 42h so far. Thing is, in the last 10h or so I have noticed the rpm drop during run-up has increased. It is still within the Rotax parameters, but I am trying to understand why it got worse. When checking the modules (“mag check”) during runup, one module drop 250rpm, and the other drops about 120rpm. The max allowed is 500rpm in a single module, so it is ok, but I am worried that the difference between each “mag” is around 130rpm (max allowed is 150rpm). It is still a pass on both, but why is the difference so close to the max allowed? The airport is busy, so it takes some time on taxiing, and the airplane is used for flight training, so overall it ends up running rich for more time than it should. We use avgas. So I am thinking one of the plugs might have deposits and not producing an efficient spark. I will try to let it run at 4000rpm for longer next runup before doing the “mag” check, see if the spark plugs are a little cleaner and the rpm drop is lower. I was also advised to take the plugs out and check if there is enough heat paste on the threads. Also heard it could be carburetor (they were synchronized at the 25h, not sure if that could have caused it). Anyways, for now the rpm drop is still under the parameters, so unlikely to be any issue with coils or modules, but wondering if there is anything else I should look at. Appreciate any guidance or insights. Tks!