Originally Posted by LW50
Understood, still almost positive it's opening rather than closing.
It honestly never dawned on me to check if the previous owner put in a JB4, so I just ran outside to see if the steering wheel menu would work--no dice. While I was there, I grabbed a quick video of the sound, you can hear the valve open up right at the 28 second mark. It's the same behavior on both cold starts, and after the engine's been up to operating temps.
You can't really hear the difference in the exhaust tone at idle and during the quick blips because the mic on my phone sucks, but in person it's noticeably lower in tone.
I'll go clamp the line one of these days to verify and rule out the possibility of myself being an idiot.
You could do a visual check. If you look down the left pipe with a torch you can actually see the valve. Just don't breathe in the fumes LOL.
Another way that you can check is once you believe that it's open/closed you can just pinch the valve with your fingers to cut off the vacuum and see what happens.