I have base 991 without PSE. However, when in Sport Mode, the exhaust seems to me to sound stronger than in normal mode. Is it only my imagination, or is the exhaust sound changed by activating Sport mode?

 

Sport mode changes the tune and idle as well as throttle response, so what you're hearing is that.

 

You are hearing the piped in music of the engine intake, it's called the sound symposer and most of us have plugged the device as it drones

 

If you are looking to wake it up, I would be more than happy to assist you! A perfect set up on a non-pse car would be our center muffler bypass x-pipe in addition to the side Maxflo mufflers or Supercup!

Take a look at the current 991 product line and please let me know if you have any questions!
Porsche 991 Product Line

 

How is the drone with the Fabspeed X-pipe system including the center and side muffler replacement?

 

+1. The valve opens up and lets more engine/intake noise enter the cabin. Unlike BMW's Active Sound Design, you hear actual engine and intake noise.

 

The Supersport X-Pipe is an aggressive system that favors the higher RPM's. Our new Valvetronic Exhaust System may be an option for you as well to gain the best of both worlds. With the valves open it effectively bypasses the center and side mufflers and dumps the exhaust out of the tips. With the valves closed it forces the exhaust through the X-Pipe and our side Maxflo Mufflers!

Take a look!
Porsche 991 Carrera Valvetronic Exhaust System