I have thought all this through prior to designing the system for the mk2...and I think i can see your problem:
Basically its because you have an open circuit with regards to the swirlpot.
The facet is a 5psi (i take it its a silvertop?) self-regulating pump, what you've got to remember is that it was designed to feed a carburettor setup.
I dont know how much you know about carbs, but the pump feeds into the float chamber, when the foat chamber is full it closes off the feed using a needle valve (or similar) attatched to a float within the chamber.
Hence when the float chamber is full and the valve is closed, the facet builds up to full pressure in the feed line, senses this, and cuts out.
However, if you using a return from the swirlpot, you will never get this pressure build up as it is an open circuit, so the facet will simply fill the swirlpot then piss fuel back down the return to the tank.
For this reason, as i said in the other thread, my setup is as follows:
TANK - (feed line) - FACET - (feed line) - SURGE TANK - (gravity feed) -RST PUMP - (feed line) - RR REGULATOR - (return line) - TANK.
In your case you are left with no option but to follow the above design, because if you want the facet to regulate itself then you need to remove the return from swirl to tank, however if you do this you must also re-route the return from the reg, cos if you leave it connected to the swirl without the return from swirl to tank you will get a massive pressure build up and summat with go bang.
My method should work perfectly, as is it a closed circuit, and its also in my opinion, preferable to the in-tank swirlpot method as you can mount the surge tank wherever you want in the car, thus making it easier to gravity feed the pump (i fear i may have problems with this in the mk1, as the car is so low and the rst pump has to be below tank outlet level!
)
Hope this helps you mate, not that you really deserve it!...
-Paul