When I was diving a KM with the CCR mod I just exhaled through the nose like usual, got the same results. The KM did hold air better than a standard mask but eventually air leaks around the seals. You said you hadn’t dove it yet, make sure you practice removing the mouthpiece section and putting it back on a lot. Also make sure the nose blocks work for you, I eventually gave up using the mask because I couldn’t reliably clear my ears using the installed system, it just didn’t work well with my facial features.