Okay need to check if this is normal. I have a 2005 911 C2 Cab that I bought CPO with 17,000 miles and now at 20k. When I first start the engine from cold and it is idling in the garage I hear a slight burbling sort of vibration noise coming from the muffler(s). Can't tell if it is one or both of them. Hard to really describe. Just not the smooth even sound of the engine firing. Definitely a bit of a bark coming through from the mufflers. It only lasts about 10 seconds or so. It is consistent. Happens every time. But only when engine is cold.

Does your car do this?

 

Very normal.
There are lots of threads on this....some people like it, some don't.

 

I wish mine sounded like this all the time. That is the highlight of my day. Again in the parking deck in the afternoon, sounds great with a blip of the throttle. I wonder if it has anything to do with the time it takes to create backpressure in the exhaust system?

 

I wouldn't be surprised if it had something to do with an emmissions device, perhaps an air pump...

 

sound lasts as long as the air pump is on for, deffinatly due to the extra volume of air being shot into the cats

 

+1... God how I love this sound... here is a stupid question, is it possible to keep this same sound on all the time?