The worst that could happen if it stays open too much is that you run rich because it is letting out air that has been metered and fuel has been injected for.
Or maybe the really bad thing is that you run like cr@p
I have heard of this splutter noise(anthough he said mouse fart) from another user who decided to get rid of his.
Yours sounds particularly bad.
I would call TXS tomorrow - their tech support of their products is great. I'm sure they don't want you running like that!