So yesterday i was driving on the freeway, and when i tried to pass some one it made a really loud bang almost sounded like a gun shot. I was around 3,000rpm when i let off of the gas, and thats when it made the big bang. what could be causing this? i have no cats on my car. this is a picture of my exhaust could it be the lack of tailpipe?

 

no... what you're experiencing, i believe is unburnt fuel getting into the early part of the exhaust and lighting off.. since you dont have cats, and you let off the gas, or decellerate the gas still pumps a few milliseconds..

have you installed a cam or messed with the tune or had a custom tune done? if not, check your fuel injectors for one sticking, check your fuel pressure. thats where i would start