cupcake.
In my opinion, thru my own experience, only mouth leaks cause the LEVEL of leaks you are registering.
If those were mask leaks, you would have no doubt about it, cause you would be having a windstorm coming out of somewhere!
And mouth breathing is very common.
One way you could verify for sure, is to tape your mouth closed.
I do not condone fully mouth taping, but for a trial, it would end your mystery.
Also, mouth breathing really does affect therapy, but mostly your chemical balance of CO2 which causes problems whether you use CPAP or not !
Check out resources on this topic.
It may or may not be affecting you, i suspect it will have some effect.
Also, it is possible that with higher pressures you will mouth breathe.
That is a catch 22, viscious circle type of thing.
For me, doing exercises to avoid mouth breathing is the way to go.
And for me at least, i get rid of a lot of mouth breathing using a full face mask, not popular but it does work and i have some threads and posts to explain that.
Hope this helps.