Plenums allow similar power to be produced with a performance package on less boost, as seen on numerous turbo powered cars over the years. Most aftermarket plenums available for the Barra engine will flow the same as the lower half of the plenum will be the restriction. Don't forget, all these plenums use the same/similar design base plates so no matter how much air is pumped in one end it can only come out so much at the other end. Some will vary in terms of throttle response & down low torque due to volume, but top end power wont differ SFA. All those out there saying plenums are a waste of time & wont make a difference obviously have never run one & are too tight fisted to get one. I say leave the flow testing alone as it wont be of much benifit.
