It does have a flapper/actuator. Not sure on the specifics about when it engages but it sounds like it's related to throttle position similar to a Corvette (you can rev it while stationary and it doesn't engage but if you're moving and giving it significant throttle, it will). I haven't done a ton of tests but the R seems similar. In motion it really comes in around 2,500 RPM.
Here's a picture (this isn't my car, I found this on Google):
You can see the right-most exhaust tip is connected to the actuator. I'm not sure if the muffler has two chambers (one with less restriction) or if just opening an extra exhaust outlet increases the airflow and sound. An expert would have to tell you, and I am not one.
(A side note: That guy accidentally photographed his head. Lol.)









Took it through some of the back and country roads around Graham and Burlington to enjoy the car. Nothing really new to report here. Averaging 25 MPG with a few heavy foot moments (you have to do this). Now that I've gotten used to the feel of the clutch and the transmission, I'm more comfortable with hard shifting. Car kicks you in the ass when you do a hard shift into second and again into third. Maybe it's just my imagination but that seems to be an AWD thing. There's no tire chirp of any kind, just pure grip.

