[jeepguy1948]

I too would be looking for an exhaust leak. There is no question that when you let off the throttle on a carbuerated motor un burned fuel is going to dump into the exhaust. Normally, this is not a problem as the heat in the exhaust keeps the fuel evaporated (gas in a gaseous state LoL) and it goes out the tailpipe as “emissions”. The gas stays as a gas and doesn’t ignite because there is not enough oxygen in the pipe and muffler but then a leak comes along and oxygen enters the system, then that fuel ignites and pop, pop, pop. A guy in our club has a device that blows smoke up from the tailpipe and the smoke comes out of the leaks. Also, some folks don’t realize that the pipe hanger behind the muffler is supposed to be loose so the pipe can slide for and aft as it heats and cools. If the pipe can’t slide then it binds up and puts a lot of stress on the pipe to manifold connection. Even if everything is perfect the exhaust manifold itself will sag at the rear (it is red hot after all) which will stress the pipe manifold connection. I did see an Aries muffler once that had a pinhole leak where a baffle is welded to the housing.