What causes popping on a stock exhaust system?

I have a manifold gasket leak if that helps. I get a lot of popping after reving. All exhaust is original and the car has 55k miles, but is now 10 years old.

That would be it! the gasket leak, you may want to check, you may also have a crack in one of the welds on your pipes or a hole. most likely its the gasket..

If you have an exhaust leak you will want to get it fixed. I had the rear bolt on the exhaust manifold break off in the head. It had a horrible leak and so i put in Pacesetter Mid's and it doesn't use that bolt so problem solved. Reach in and feel if all 12 bolts are still there and then recheck them to be sure there tight. I had the one for the Alternator bracket that was only hand tight. It was a great way to convince the wife that aftermarket headers were necessary.