On my journies thru different sleep forums, I see many people saying it's too hard to exhale with their PAP therapy. I just posted a topic at the blog site: www.sleepandcpap.blogspot.com that touches on this issue and its remedies.
I don't have any problem exhaling, I can even cough into my full face mask. BUT - I can't burp up the air that I swallow in my full face. So I pull the mask off my face to let those burps just rip away.
Sorry, SleepMBA, moi bad, but I just couldn't resist.