popping isn't created or stopped by the exhaust. It's only made more noticable.

if you want to get rid of it, you'll need to get something like the interceptor-x and lean out the afr. The car stock is almost as rich as it would be if it was a FI engine. My AFR's are in the 10-11's in the upper rpms.

 

if the car is fully warmed up, it should pop less. When it's newly started, the engine is dumping fuel on the cat to warm it up. So when I start up and drive a few feet then let off the gas and coast + engine breaking, I can make a dozen or more popping noises. Once it's warmed up that doesn't happen unless I rev it up - and it only pops a few times.