Its kinda hard to diagnose without actually hearing it. Where is the sound coming from? Have you checked all of your exhaust pipes and manifold connections to see if you might have a leak somewhere? Can you take a short video of the sound and post it here?
Have you checked your spark plug wires?? If there's a break in one of them, you'll hear it clicking above the exhaust manifold if it's broken near one of the spark plugs...and your exhaust will be choppy since it's not getting the spark it should be. Check your wires and plugs.