If your ignition module is going bad, it can cause a weak spark which in turn can cause a rich exhaust . Because G bodies are prone to be screwed around with by POs, make sure it still has the stock computer advance dist which should lack any vacuum advance and make surd the 4 wire computer anvance fonnecter is plugged in and not damaged or messed up. Saw one guy who had a MC with the stock computer carb but had the stock dist swwpped out with a vac advance one by the PO for reasons beyond logic.
