hi, im upgrading my hitachi carb to a weber,and have discovered the abscence of a return to tank line. instead what seems to be the return from the hitachi goes through 2 little 'canisters',one of which seems to have a vacuum conection. i was wondering what these are. the pipe from these just terminates in the engine bay with an open ended pipe. would i connect the return from the weber to this system? i thought i might just blank the return. cheers