fuel pressure drop

71 duster with a MRL build 408 dropped in

a while ago I took her to the dragstrip for the first time and noticed she was running out of breath so I decided to upgrade the fuel pump

I installed a carter M6270 mechanical fuel pump , a filter a pressure regulator and a gauge
(in that order)

I had the regulator set at 6 PSI but noticed that after a while it dropped to 3
I decided to clean the filter because I had "back bled" the tank vent line and i thought i might have some crud in there from doing that
it turned out I had a LOT of crud in there, so it looks like the filter did its job

then i realized i was being an idiot for installing the filter AFTER the regulator because probably had some crud in it aswell (which it did)

so, took the whole thing apart, cleaned it, and flipped the bracket around so i could put the filter between the pump and the regulator

hooked it all back up and fired it up...6PSI
let it idle for a while and it stayed at 6
so i went for a drive and when i got back the pressure was down to 3
i tried adjusting the regulator but could not got a different reading

i popped the tank cap off but didn't hear a "woosh" and no change to the gauge

then i jacked up the rear end to look at this flexhose i hear people talk about collapsing

what do you guys think, could this be my problem ?






and if that looks like it needs to be replaced with a slightly shorter piece, how do i remove it withouth getting showered with gas?

or is there something else that might cause this issue ?

i let the car cool down for about half an hour and when i fired it up, it read 6 PSI again