I have a loudmouth catback. When i start my car for the first time of the day and it hasnt warmed up yet, it pops and makes this gargeling sound when i lift my foot off the gas( all the time, im an m6) any clue what this is. ive never heard it on any other car??

 

Could possibly just be unburnt fuel lighting off when it reaches the air being pumped in by the AIR pump. Yank the AIR pump fuse and see if it stops. SES light will come on, but you'll be fine, and you can just put the fuse back in and clear it (autozone for free, or do SES reset by pulling PCM batt and PCM ign fuses for a while).