Rev 318 in park, slows down and stalls..case study.

can you observe the carb inlet when you are idling it to death? Youll be looking for the normal fuel mist to stop during choking or the boosters belching fuel and the motor flooding and quitting on you. you can blip the throttle when its flooding to clear it and drive through it as your flushing the carbs transfer slots that are "under water" when its flooding into a closed butterfly valve at idle. I would suspect a plugged muffler as a refusal to run at higher RPMs. I had a truck with a very weak electric fuel pump and I could idle it all day but once I got on it it would die in a matter of about 20 seconds. But it would always start right up. same would go for a blocked fuel filter. The guy at the auto parts store said the same thing, plugged cat or muffler so I cut them off to see if it helped, it didnt but I did find that my muffler had a huge leak and the pipe had pinholes everywhere so as to fail me in the smog test.