I have a 73 Challenger 440RB with Edelbrock AVS. The engine is a stock 72 HP2. My timing is set at 16* initial and 32* total all in around 2800 rpms. With vacuum advance hooked up, I’m around 50 to 55*. I’m running 93 octane gas. I’m idling at 880 to 900 rpm in gear warmed up and 1050 to 1100 rpms in park / neutral. When I shut off the car, I get a loud single pop from the exhaust. Any ideas?