I thought it only changed the valves at low speeds, HOWEVER it also open and closes the sound symposer in the upper RPM's. There is definitely a volume difference on throttle in the upper RPM in the cabin from the intake sound going between Exhaust off/on.

Having compared both, I will not be doing the sound symposer delete.

 

Yes it definitely adds an element to the upper mid and high rpm range. It’s even more accentuated with an aftermarket exhaust. I’m not sure how much the sound symposer would detract from that but I didn’t want to mess with it either.

 

I also noticed this after installing my JCR rear exhaust.