Just a clue on the cutback while taking off but not on a static thrust check: The takeoff has a sporty acceleration that throws the fuel back against all surfaces (tanks, filters, fuel lines, header tank) so there could be some readjustment of the stuff that forms the blockage that wasn't seen statically. An acceleration of about .2 Gs (4 knots per second) will "look" like a 12 degree upslope to the fuel system.