Backfiring through carb, what could be causing this??

[benbloom]

hey guys, since i got my truck ive had this problem of occasional to not so occasional backfires through the carb. at first i blamed the carb, but 4 carbs of doing the exact thing i am sure its something else. i got my timing adjusted by a mechanic recently, and ignition system is supposedly running fine. could it be the distributor? or something in the engine? i am assuming its not how my carbs were adjusted because they have been adjusted by different people and different ways. anyone have this problem? let me know, this one has left me scratching my head. thanks!