I've noticed the last couple times I've driving the Dart (mild 360), the exhaust is getting really potent - burns the back of my throat when I'm driving .. it's also got a little bit of a stumble off the line, and every now and then if I jump on the gas after sitting at a stop light, it'll give a pop out the carb.. sounds to me like timing? I had it running really good, no stinky exhaust.. but lately I've been noticing it getting worse.