I have read that if you use a external venting bov, this will cause the ecu to read a false picture of a large increase in airflow. Which then leads to an excessively rich mixture.

I have also read that using a cai or short ram filter on the wrx will cause the motor to run lean.

Would using the two together zero out these effects or worsen the rich mixture? If the later of the two, would opening up the exaust side of the picture help to lean out the rich mixture
without upgrading the ecu?

Any thoughts?

 

With a CAI you'll run lean all the time. The BOV will only make you run rich following venting, so at best you'd run normal for a few seconds at a time, but I doubt they'd even each other out anyway. Get rid of them both.