Ok I need help. I have a Briggs and Stratton 19.5hp opposed twin engine with fuel issues. I am able to start and keep the engine running as long as I poor gas down the carb. Therefore, it must be a fuel pump problem, however I have replaced the rebuilt the pump, and when that didn’t work I bought a brand new carb with pump on it. So that didn’t work and blamed it on maybe getting a bad carb/pump and returned it and got another one. Well same dang problem. I have tested the fuel line and fuel runs freely, I have opened up the carb and poured fuel into the bowl and it will until that gas runs out. I have tested the vacuum line and air is moving to the pump. What am I missing????