alright i have problem that is becoming ennoing when and only when i fill up with gas and leave the car running or turn it off i alway have a problem with it getting enough fuel i though maybe it was all the time but i took off the fuel cap and tightned it back down one day and it still did it now i am becoming concerend b/c i have a built motor and i am afriad that if i fill up with gas and start it it something might go wrong b/c it not getting enough fuel also once i start it and drive like a mile or two it has a enough fuel pressure to run fine bt when it first start the fuel pressure is real low

i ahve a new walbro 255 fuel pump less than a month old
and stock injectors
stock gas cap
fuel rial AEm
new fuel filter

if ay body has any sugestion of wat might cause this problem plz lmk ASAP thanks in advance