I'm hoping someone can help me. I have a Pari Proneb Ultra and a Pari Proneb Ultra II (one for use at home, and one in the car). The Ultra II has never worked as well as I expected and takes much longer (25 minutes for Tobi versus 15 on the older model). I use LC Sprint nebulizers with both. The Ultra II has been cutting on and off, so I'm probably needing to replace it. Does anyone know if those Ultra II's just don't work as well, or did I get a faulty one? I have found good deals for both models and can't decide which way to go. Any help would be appreciated!