I never had a stock exhaust before, my last 996 came with PSE and I didn't really notice any sound level change over the 3 years or so I had that car.

On my new 997 C4S with stock mufflers, I'm now at about 1300 miles and unless my brain is playing tricks on me I swear the sound is a bit louder. Not a lot louder, but enough to be noticeable.

I'm wondering if that is just a trick of the mind because I've been driving more aggressively lately and breaking in the car above the exact book specs of 4200 rpm, or whether the stock mufflers break in a bit to become a bit louder than brand spanking new?

 

Hum...I think it's playing a trick on you! Most exhaust will get louder over time.....but not over 1300 miles!! It will also be hard for you to notice since you drive it everyday...

 

It is my understanding that new mufflers do break in over time as the sound deadening material inside them goes through numerous heat cycles. I know that my car sounds louder now after some 6 K miles than when new and my son has noticed it also when standing behind the car.