If stage one on the 545i is 8 hp, then no. You'd need probably double that to be able to truly feel it in the seat of the pants. Your cars' hp output can vary by more than 8 hp depending on the weather/temp changes alone.

 

Basically all it does is tells the car you are pushing the pedal farther than you actually are. It in no way increases the actually performance of the car.

In my opinion $300 for a device that pushes the pedal harder for me, isn't really worth it.