The main fuel feed on a Sav comes out under the fuselage then through a tap on the floor then it goes out a 10mm alu pipe under the front floor and the metal pipe does almost right angle curve then direct up the firewall and mine then went to a gascolator. I found it by checking the gravity flow from the tanks to the gascolator and kept sectioning until of course the last piece of pipe was the one curved around the firewall from under the aircraft. I took that piece of pipe out and blew the compressor through it and out popped this bit of white plastic about 8mm x 12mm and it had got caught in the curved area and half blocked off the pipe...took a while to find