606 engine quits

I will check again for a manifold leak. I have some fresh oil around the exhaust manifold which suggests that may be leaking but is no noisy hot air coming out suggesting an exhaust leak.

One way to check for an intake manifold leak is to take a spray can of starting fluid or carb cleaner (carb cleaner may be safer) with a short tube stuck in the nozzle and spot spray all around the manifold and carb gaskets, etc. If there is a leak that is sucking air, you will hear the rpm's pick up when spraying at the leak.

This is a trick I learned regarding leaking vacuum hoses on new cars and trucks. Spraying around leaking, cracked, etc. vacuum hoses will cause in increase in idle. You can then isolate the cause.