BB turbos do spool fast but most of the time you will find people (even race car drivers) using a non-BB turbo. remember the bigger the turbo the longer it will need to spool up. honistly i dont see the need to buy a BB turbo unless u have a turbo the size of a basketball. a t3/t4 or even a t4 wull spool up around 3k-4k rpm maybe even a little sooner