Wood - did you clean the wet side as well?....would be a good exercise - but I'm sure you did.....
Great result - these 2 numbers are very important...even though they may only be "indicative".

To put it relatively.....9 minus 5 = 4" WG - lets say its 250cfm.....
pressure drop quadruples for every doubling of velocity (cfm in this case across a constant cross sectional area) so at 500cfm the drop would be 16"WG and at 750cfm...(for a 6000rpm 20psi) setup = 32" of WG or about 1.2psi (8kPa).
Putting this into some other perspectives.....

At 750cfm, the needswings intakes are reported to yield an improvement of 20"WG...over stock. You can recalculate that from the data presented by Needswings here.
https://www.crossfireforum.org/forum...tml#post374823
that change is worth about an 8rwhp gain.

So gains are diffinitely there - we gotta find a way of cleaning these without a remove/install.

In ref to "push/suck" comment - they are not different actions...they relate back simply to pressure differential - they are the same thing - simply pressure equalisation.