Carbonio itself doesn't make as noticeable a sound (I'm assuming you want the blowoff sound) as the Neuspeed or other larger intakes. However, the engine definitely sounds throatier at higher RPMs when sucking in more air. I get the blowoff sound, though, because I bought a new Forge diverter valve w/ the spacer when I got my ECU reflash. It sounds pretty sick! >
I drove along another gti on the street today and we talked a little at the red lights. I could hear he was using a blow off valve that sounded really bad ass but I think it's a little to rice for me. Besides from what I have read the turbo in this car uses that back presue to keep the turbine momentem. so I gues this would increasee lag.
I've heard a lot of assumptions regarding the BOV. I've heard what you say, but I've also heard that the atmospheric BOV allows hot air to be released rather than allowing it to spool back through the turbo. I've also heard that the reason the GTI uses a recirculating BOV is because mainstream consumers don't want a loud BOV sound...that's for a select audience. Long story short, I haven't heard anything concrete regarding that. I know I have it, and I don't notice any difference in turbo lag whatsoever. I love hearing the "PSS" when I let off the gas after working my turbo hard! O0