I'm using one of the FCP fuel pumps (made in Italy with a replaceable diaphragm) without a pressure regulator because I wasn't aware there was an issue. That said, I've had no other problems with it, except that it revealed a fuel hose that leaked because of clamp wear. I have a Pierburg on another car which hasn't given me any trouble either, but at start-up this Spring one of the bowls flowed over, which had never happened before. Adjusting the float a bit and making sure the needle tip was clean fixed that. I have a feeling that the FCP pump (the same, BTW, that ipd sells for about the same price) shouldn't give any problems, even without a pressure regulator, as long as the float valves are in good shape and the floats themselves properly adjusted. Of course, time will tell.

Bob S.