A while back, we blanked/deleted the blow-off valve, one effort among many to nail down a boost issue.
You can hear what my BOV used to sound like in this video at approx the 11-12 seconds mark. Kind of a ppbblblblblbltt (whoopi-cushion-like) rather than a PPSHH!
We opened up the BOV this weekend: The piston inside was completely stuck. It took alll kinds of hammering and bashing to pry it out. Previous Owner (I'm assuming) put a couple of metal washers inside - to harden it, I guess? More resistance for the spring? - and these were not stainless, so they rusted. Here are some pix of what the inside of the blow-off valved looked like.
scratched, friction, oxidation
Marks on the base of the piston - someone had already taken a hammer to this thing before, to try to pry it out. This means Previous Owner (or the dealer) knew about this and left it there.
Here is our temporary solution to fit the oil-vapors pipes (across the intercooler) across the BOV's trumpet, until we have time to pass some tubes underneath it instead.
And now here's what my BOV sounds like (like it should) at 50/50 recirc