Yup, blow off valves do help your turbo life and also help the boost come up quicker when you let off during a gear change. When your boosting hard your turbo will retain its momentum because of its mass and because its spinning at close to 140,000RPM. When you lift off the throttle, your throttle body closes, and the turbo, which is still spinning suddenly finds that there is no place for the boost to go. So the boost stacks up in the intercooler, your plumbing, and the back pressure will reach the turbo compressor wheel. All that resistance will slow your turbo down alot and quickly, stressing the bearings and the shaft. In the worst case after 1000's of miles you might twist the shaft completely. So we throw in a blow off valve, which is basically a pressure relief, and life is good. Now when the boost starts stacking up when you go from boost to a throttle lift, the BOV gives and the excess pressure is exhausted. The beautiful pissssh! The performance advantage is that the BOV keeps the compressor wheel spinning. It can free wheel, more less, and hold it's rpm. So now when you get back on the throttle, your turbo doesn't have to recover because it lost speed when the boost staked up and spool up to operating speed again. Now your boost is quicker in arrival, and you go faster. Besides that it just sounds cool!
LOL...note to one's self......I get alot of spelling mistakes at 3am in the morning. I hopefully fixed them all!
