Fuel pressure?

I've some suspicion on the diaphragm mechanical fuel pump on VW 1302 Super Beetle, because the the fuel filter in a transparent plastic case shows the unstable fuel supply to carburetor, sometime filled with fuel and another time empty inside?
Unstable idling may be caused by the unstable fuel pressure by the Brazil made diaphragm pump?

Judging from the Web site information, Mitsuba 0,2cc/sec electric pump for carburetor model may be suitable for VW 1,600cc AD OHV motor.
As a countermeasure for fuel supply I would try this in future.
This kind of pump should not be mounted in the engine room but outside because of the heat.

Not a little attempts are left on my VW Beetle before giving to my son.