They are a one-way clamp, what we've always called oetiker or squeeze clamps. To undo the one that you are speaking of a narrow bladed screwdriver slipped right down where it is squeezed together will work. Work the blade tip in and then back and forth to spread it and then you can work it around the sides where it can be released. Normally you would just cut them off with a nice sharp set of dikes or cut through it with a die grinder but seeing as how that one is set right ontop of the breather box it is kind of tough to get the aforementioned tools on it. As far as setting a new one goes, a set of end cutters should work good. Because I do this for a living I have the correct Oetiker brand pliers that have both angles on them.

Mark