May I suggest when your running water thru your flushing port, take a can of compressed air and blow thru the tell tale hole, myself I use my wife’s compressed air for her computer she’s always asking what happened to the air for her keyboard I say I don’t know, hope she’s not reading this??!!
Have your injectors cleaned by a professional, I have a 2006 150 and the same thing was happening to me, I took the rail and injection to a professional injector cleaning outfit, and I get 5600 again, before the cleaning was 5000
Hope this helps
Jeff