Hi i have a 97 chevy suburban k1500. Set distributor...cam retard reading 0 & +1 but I'm hearing popping from tail pipe. What could be happening? Do I need plugs?

 

Pooping from the muffler or exhaust system is usually unburned gasoline igniting. The misfire allows the fuel into your exhaust. Your P0300 means you have a misfire in one or more cylinders. Could be plugs or a bad coil as well. Might also be a good time to check your cylinder compression levels