My 997 2012 GTS has been at Porsche shop for 3 days, and the latest status... they're still diagnosing the problem. They did throw me a tid bit of vague detail, apparently, they found a leak in the vacuum hoses. Great. So, it's in the shop, and they have no idea when it will be resolved.

One good piece of news is that the tech believes the flaps are definitely stuck closed all the time which means presumably when it is fixed, pushing that sports button will reveal an even more amazing sound

Fingers crossed and waiting is torture.

 

I have found that the more aggressively you drive the car the more the valves tend to open. It almost seems like the computer learns your driving habits and adjust to them. After an aggressive run I noticed that the flap must have been open more and was much louder than normal. It also seemed like they open sooner when driven more aggressively. Could just be my imagination.

 

I feel your pain. My GTS had the same issue. A local Porsche dealer's master mechanic took 4 days! to resolve. He had to drop the engine! I was terrified. According to him, after replacing about 6 vacuum pressure solenoids, the problem was solved. Asked why this would happen after less than 30k miles, his response was....it happens. Ok. The valves were perpetually closed, and now they open at touch of that button. All is good.

Next step... Sharkwerks center muffler X bypass.

Good luck .