I think that I determined that the check valve in the main vacuum line was causing the issue. It was only pulling a few pounds of vacuum through that valve. The other vac connection pulled quite a bit better, so I took the lines off the check valve connection and joined them to the other connection. Car shuts off now, so the main issue is manageable for the moment. I will be ordering a new main vac line and then put stuff back like it was once I replace that.

I have a question regarding the fuel shut off valve however. There are three vac connections going into the switch. A brown line that goes to ign, a vac line that goes in the top, and then there is another short, 90-degree hose comin out of the side. This was not connected to anything (in my case) and I did not see any vacant lines that may have come disconnected from this. Is this some sort of breather line or something? or should it be connecting someplace?

Thanks!