No place to run the pipe as the fuel tank accommodate the whole right section of the car up to the bumper... So best bet is to route a channeling pipe inside the rear bumper cavity. Requires some heat proofing, if not your bumper will get very hot.and since e34 bumpers are fragile, it might crack.
Unless, put a dummy pipe there. glue it straight from the fuel tank, as there's no suitable metallic place to weld it on.