"Very true, but we're mixing the pews in the church.
High compression ratios's are not necessarily required for high VE"
High CRs enhance cylinder fill because the overlap cylinder fill becomes more efficient. With less volume to pull on, the exhaust pulse vacuum can pull more fresh charge earlier increasing overall effectiveness. With the overlap period creating up to five times the draw of the piston at max velocity any change to the package is significant. Look at the latest Hemis, 10.4 or higher compression, big intake ports, very long tuned intake runners, short cam. It all has to be right, but then the power is amazing.
As to how much exhaust tuning helps, I think most know it is huge. Look what happens to hp when a motor is run with Zoomies. If there is no tuned length etc, power goes way down.