now you asked for it
my first point of ass kicking comes from your idea they reduce turbo lag. A blow off valve is designed to release compressed air after throttle/and or boost has been cut. The reason it does that is so you dont have too much pressure on the turbine. When you release that air into the atmosphere you lose all of that pressured air.
Since you have released that air that has been already read by the MAF- your engine now thinks it has enough air so when you reapply throttle it dumps too much fuel into the cylinder and not enough air. Thus causing you car to bog down as it tries to deal with burning that fuel. THUS NOT ACTUALLY REDUCING TURBO LAG, BUT INCREASING IT.
Now on too your second point. Why would the car's blow off valve(which btw- discount tires rx8 doesn't even have) be realeasing air when under full acceleration. The noise you are hearing is the turbo compressing the air. When he lets off you hear a mix of diverter valve which produces a mild whoosh sound, and a high pitched squeak which is wastegate chatter. The reason you here wastegate chatter is due to the fact that he runs open dumps to atmosphere. Which is also why if it were nighttime you would see small flames coming from the bottom of the car.
So lets bring this full circle- you can use a reciprocating diverter valve if your smart- which stores the air already read by the MAF so that when you reapply throttle the motor is running perfect, or you can be an idiot and run a BOV.
The only time when a bov should even be attempted is in monster drag cars that build enough pressure to actually damage the turbine and compressor housings. Even then most are still running- you guessed it- a diverter valve.
YAAAAYYYYYYYYY
