Fuel pressure gauge is an easy buy, visit a shop which sells air-conditioning equipments, ask him to give you an low pressure line air conditioning gauge. Attach a small rubber pipe used for connecting gas heaters with gas valve in homes, few similar clips to tie the pipe and your pressure gauge is ready.
Then use OBD to find short term fuel trim and long term fuel trim as these valves may give you a good idea if vehicle is running lean or rich. You can’t be sure, that’s it’s an issue with fuel pump or fuel filter before you perform a fuel pressure test.
If car is running lean then problem at times seems to be resolved and comes back to haunt to later after day or two. This is a tricky work, you also need to know what controls the air to fuel mixture in your vehicle, like in new vehicles it is controlled by O2 sensor and in some old EFI vehicles this is done by variable resistor.
By default replace PCV valve after buying from scrap yard, stuck open PCV valves can result in car running lean. Answer provided is sufficient to diagnose an issue with fuel line, rich or lean conditions with vehicles provided you follow what’s been told.
