Yes, I noticed changes in sound and performance.
Sound improved dramatically, to the point where I'm sure my gas mileage is suffering because I can't keep my foot out of it.
Listen here and look in the description for the key time frames.
As to performance, the additional flow makes it rip from 3,800 rpm's and up. You can feel and hear a big change.
As to lower end torque loss, I haven't noticed it, I'm always in the higher rev ranges to enjoy the sound.
The sound is especially magnificent when the top is down.