[ he almost--almost opens his mouth to ask if Waver if he was joking.

But hearing a large crash behind them, trees being... rended?? apart?? as something big thrashes around back where Waver threw a flashbomb??
Nope
there's no need to confirm that this was, in fact, not a joke.

Vash is kicking it into highgear, and he's immediately running a bit faster than he was a moment before. ]

--Hugely smart thinking on your part, but how long you think till it starts chasing??
Flashbangs usually piss big guys off!!!