I ordered a 6 volt electric pump to get me rolling while I find (hope to someday) a replacement vacuum canister. Its the lowest pressure (I can find) available, 2.5 - 4 PSI. Does anyone know roughly what PSI these gravity fed carburetors can handle? It is suppose to be internally regulated, so I should not need a return line. Just wondering what other guys have done. I may try and choke it down with a needle valve if I have to.