I have a 2006 chevy silverado 1500 4.3 v6. I had two check engine codes. The first one was for the oxygen sensor in bank 2. I replaced the sensor and the code went away. The second code was from multiple misfires. I changed the cap, rotor, and wires and this made that code go away. Now there is a loud pinging noise coming from the passenger side of the truck. It seems to be coming from the general area of the flex plate or y-pipe of the exhaust. The noise is not present at idle. Only during the deceleration of a rev does it start. After driving for a bit it will go away. There are no check engine lights on anymore. What could cause the pinging noise?