Fuel pressure issue

check it with the fuel filler cap off. if the tank vent or filler cap doesnt let air in when the fuel is leaving. your pressure will drop from there being too much vacuum in the fuel tank. sometimes one can hear the tank make a clunking noise from it being sucked insideout. ive seen spider webs plug the vent lines before.. and usally if thats the case, after the car sits for a bit the fuel pressure will come back up for a sort time then drop again..bubbles in the fuel filter can be caused by the tank trying to get air through the fuel line backwards past the needle and seat