Popping sound in headers

Wondering if anyone can tell whether or not I have a problem here. 340 w/Hooker comp headers makes a popping sound like small backfiring in the headers (or maybe a bit further down around the collectors, hard to tell) while idling before it is warmed up. It's pretty random and not frequent, maybe evry 20-30 seconds or so you'll hear a muffled "pop" type sound. Goes away after warmed up. Unknown cam.

What could be causing this, and do you think it is a problem I should look further into? Car seems to run fine, no other problems noted.

Any advice welcome, tks...

Paul