One of the foundations of fluent speech is proper airflow. It is no surprise that when you're stuffed up, you're going to have more disfluency. Unrelated to stuttering : Are you sure these are colds and not allergies? Have you tried a neti pot? They typically don't work when you're already stuffed up. But once you're clear, start using the neti pot. They do help remove allergens and irritants. My general sinus health greatly improved after I started using the neti pot. And I only use mine infrequently now. When I have the first inkling that I'm starting to get stuffed up. Or if I've been doing a lot of work in the yard that day and have sinuses full of dust and grass and what not. If you do start to use the neri pot, please make sure that you follow all the directions. They're simple, but for some reason people think that they can do it without the salt packet, or use questionable water sources.