Thump at idle

[B7A4AWD]

Just had a question for you guys. When I'm sitting at a light or drive through, and I'm just idleing, I can hear a thump coming from the trunk area of the car. Possibly muffler related, but very strange. It's not consistent at all, and sometimes will thump louder than others. (My stereo is turned off by the way). Any idea if this is a normal thing. I believe it is coming from the mufflers, but just wanted some feedback.

Thanks,
Shawn

[B7A4AWD]

Bump for any ideas.

[kristokes]

possible backfire? ru flashed at all? if you are im going to guess APR.

[B7A4AWD]

No flash, car is still stock. I never even thought of backfire. It's not very loud at all, but I guess it could be a minor backfire. That makes me wonder what the heck is causing this then.