1. The idea of at the push of a button you can switch between quiet and racing mode is a feature.
2. Where other exhausts are always loud Borla Valvetronic Exhaust Power valved systems allow you to switch to a quiet mode.
3. This Normal quiet mode is usually the same as a stock unit by restricting the exhaust flow.
4. With the exhaust valves open, the system roars giving you the performance and sound you desire.
5. Motosport also provides these valvetronic exhausts for the BMW M5/M6 V10, Nissan GTR, and the other high end cars.
It's possible that the product is relatively new or not well-known, or that there simply hasn't been a review posted yet.