I think you should read up on how turbo cars work before you purchase one. Please dont take that the wrong way, everyone has to start somewhere. a blow-off valve and or bypass valve "lets off" or Opens up" upon a major vaccum change, so anytime you let off the throttle, the blowoff valve may open partially, fully or not at all depending on many different factors.
Most people who dont own a turbo car or know how they work, think only manuals let off when the gears change, this happens because you let off the throttle, then push in the clutch and shift gears. the SST in the MR makes it so your turbo does not have to respool after every shift if your not great in a manual trans. In a automatic turbo after you build pressure or boost and let off the throttle the blowoff valve will open, depending on the setup, car and blowoffvalve will depend on how fast or easy it opens up. Sorry for my long reply, I hope it made sense without getting super techinical and I'm also exhausted.