My VW 1.8T had a similar setup to these, and lot of people replaced them because the stock part was weak and often failed under increased boost. We called it a Diverter Valve (DV), it serves the same function as a Blow Off Valve (BOV), it just vents the excess boost differently.
DV's are used on cars that have Mass Airlfow Sensors that measure all the incoming air, which is used to calculate the correct amount of fuel to use. It's important to not vent out air that's already been measured because then your air-fuel ratio gets off, and bad things start to happen!
No matter what a company says, unless they do some engine computer upgrades, a BOV is not going to work properly. It's just the nature of the thing. There are a lot of valves out there that offer both functions, you just have to make sure you install them correctly so you don't accidententally leave it in BOV mode.
It's true that because a DV routes the air back into your intake piping, you don't often hear them. I couldn't hear my VW's at all, until I put on a CAI. Then it was just as loud as most BOV's, it was fun to scare pedestrians with...
I have not yet heard of any rampant problems with the MSP's stock DV's, so if noise is all you are looking for, it may be better to put on a different intake instead of messing with the valve. A free flowing intake lets more air in, and more noise out, so it will make a big difference.
That being said, I swear I can hear the DV in my new MSP. The car isn't broken it yet so I haven't really gotten on the gas, but when I am accelerating quickly I'm positive I can hear a little release from the front drivers side, right where the intake is when I shift. I can't wait to break in my car so I can find out if that's what I'm actually hearing or not...
Anyway, I hope this helps explain some things. If you ever want to learn all that you possibly can about DV's, head over to vwvortex.com and read through the 1.8T forums.