I also feel that it's a rate of speech combined with air flow problem, along with general level of physical excitement. I definitely need to slow down more as a habit since it's easy for me to forget once I'm into a conversation, but I've also tried just focusing on saying or elongating vowel sounds in various words. I've also tried taking more frequent breaths between phrases with some success, but it all tends to fall apart once I get overly excited or engaged and stop focusing on the methods. Which is funny because sometimes I'll totally forget I stutter and be perfectly fluent, but once I remember it's a possibility it also comes back. Weird stuff dude.