Brad, I agree with you, that to quantify the difference between two filters the saw should be re-tuned for each.
However, can we also agree that there is a correlation, that in general, the less restriction of the filter, the richer the tune will need to be, and the more power the saw will produce? Ditto for the exhaust? And, improving both intake & exhaust is best?
Don't know why we are going back & forth on this, it seems pretty basic to me.
As to any difference is performance from HD-2 to Max Flow, I have never used a Max Flow, I was relying on the dyno results, so I don't know the answer to it. However, I believe either one will improve the performance of your saw.