I did some searching on this too recently and found the same info and links that have been listed so far, but nothing that looked it was from any official data. 8psi does seem pretty low, but if we’re speculating that the 9-15psi range listed for other filters is the starting point (9psi) and the pressure needed to be completely open (15psi), then maybe MC’s 8psi is just the point at which the valve starts to open. If that’s the case, then there really isn’t much difference. Heck, I bet there’s more than 1psi variability filter to filter of the same design.