lastnight my car died again. it does not keep 43psi if fuel pressure after i drive it around for a while.

after it died i popped to hood to look at my fuel pressure guage and it reads 10psi

-i turn key forward to prime pump it, listen for relay and fuel pump. i can hear both

-step out side and look under hood... still 10psi

-i crank starter for a few seconds and it fires run out to fuel guage, it reads 30psi and starting to drop

-if i leave the car overnight ill start it up and 43psi

i cant take it to a shop because it will run fine so its no good to them unless it shows its face right there.

is it a bad pump?

ive replaced:

fuel pump a 7000kms ago with a walbro 255
fuel filter
relay
kirban adjustible regulator 2000kms ago

im all out of ideas