Idle/Back fire prob

[sug_high]

I have had this vehicle for about a month. I bought it off a guy who could not afford to repair it because the timing chain had broken. I pulled the cover and it had jumped one tooth, but other than that no problems. I replaced the timing chain assy and got it running. The car drives fine, except for a little miss when idling. It is not a dead miss and I know that I have a exhaust leak, but when I rev the engine, I get a little pop when I let of the gas through the muffler. I have read alot of the messages posted on idle/backfire probs and I have replaced the plugs, wires, cap & rotor. I have cleaned the contacts for the MAS and wiggled about everthing under the hood to see if it changed anything. I removed the AIV and cleaned it, took the valve cover back off to make sure that I didn't have a valve sticking but that all looked fine. I know that the guy put a new fuel pump and filter on it because that is what he thought his problem was. Is there anything else that I can try?

Thanks

[NISTECH]

do a leak down check in the cylinders to see if maybe a valve took a hit when the chain was off.