The stock exhaust on my blazer was pretty tore up when i got it. So i had muffler that i had laying around from another project welded on with a turn down now there is popping after revs and so on.. So maybe an exhaust leak or something to fix? or if its just the type of muffler which is a dynomax bullet then i can live with it...but heres a video. Srry about the poor qaulity can tfind the charger to my other camera..
Picture.mp4 Video by whitetrash_royalty | Photobucket

 

nah prolly not a leak. you'd be able to tell if it is leaking. does it sound like air is rushing out somewhere? my assumption on the snap and pop noise is because of the less restriction the gas has.(don't quote me on this)
my custom duals only do it everyonce and a while after i first start mine on a cold morning and give it a little pedal which i love because it doesn't sound like a revved out chainsaw.

 

If it's 99 or newer with the secondary air system, you probably have an exhaust check valve or diverter valve that is allowing fresh air into the exhaust on decel. Is the SES light on? Are there any DTC's in memory? If so, what are they?

 

Its a 99.. No ses light or throwing codes

 

The most common causes of back fire or multiple pops through the exhaust on deceleration, is an exhaust leak near the engine, or the secondary air system introducing fresh air into the exhaust when it shouldn't. Check the exhaust for leaks and disable the secondary air system & plug the check valves, see if either one changes the backfire/popping. During deceleration, the hot exhaust has unburned fuel mixed with it, introducing fresh cold air, (oxygen) ignites the mixture. Same reason that open headers pop on deceleration.