Just give it a squeeze after you've been on a run as a quick check.
Try it cold and it should be hard-ish to squish, but once it's hot it wil lbe a lot more pliable and could quite easily be sucked closed/flat

I think if it was the hose it would do it in all gears but you never know. Runs same boost in very gear so why would it be different in 3rd/4th?