also as far as your calculations go...the K&N website seems like an estimation of what you need. their numbers are based off a motor with 100% efficiency. at 7000rpm i really really doubt you are close to that just given the idea of typical valve events...but to just go along with it for the sake of argument, your numbers are right. but you also have to think about it a little too. the more vacuum there is, the more air is going to come past the filter. that filter at one point may flow that 600cfm you are lookin for, and you also need to take into account your PCV system if you are still running that into the intake piping because that would be another source of airflow. you have to also take into account the only way there will be no vacuum is having a huge filter and huge piping or running the turbo freely.