Starts but will not stay running

I have an aq171 and I am having an issue with it only running for a few seconds before stalling. If I pump fuel into the engine it will run for a little while then stall again. If I keep pumping the throttle it will stay running but stall if I stop. I cannot figure out the issue. I have rebuilt the carbs, replaced the gaskets and replaced the intake manifold gasket and it is still doing the same thing.

Re: Starts but will not stay running

Fuel filter? Fuel pump? Plugged vent hose?

Re: Starts but will not stay running

I have a new fuel pump, new fuel filter, but I have not looked at the vent hose. I will check that tomorrow.

Re: Starts but will not stay running

I checked the vent hose and it is not plugged. I hooked up a vacuum tester and found that I am only getting only 7 in.Hg when I should be between 15-21. I have replaced the intake manifold gasket and the carb gasket, and I am not getting a change in vacuum. I set both carbs so the butterfly valve is fully closed, and I attempted to tune the carbs using my uni sync but I get strange readings. The first carb is pulling a lot of air and the back carb is not pulling in any air. I had to close the uni sync all the way before it pulled in any air. When I turn the air/fuel mixture screw I get no difference in the back carb, and the front carb the screw needs to be out all the way for the engine to stay running. I am not sure where to go from here. I have sprayed carb cleaner around the carbs and intake manifold to look for a leak and I have not found a leak. Could this be something with the valves? I am not sure where to look next.