The fuel filter and fuel pump are in the wheel well of the right rear tire. Usually you would test the pressure at the fuel rail but at idle you aren't using enough fuel to starve either the pressure or volume of fuel. As a test I would take the car out and put it in low gear and see how many rpms you get before it starts to stall, then go to a higher gear and do the same thin. If the car starts to stall at the same rpm in each gear you can be pretty sure the fuel filter is restricted or the fuel pump is weak.