First, sorry for starting a new thread. I added this to what I thought was an existing thread when using the mobile optimized web site. So...uh, apologies to the users and admin.
To answer your question, yes to sound, and unknown to performance. I'm coming from a Triumph Speed Triple with Moto GP style low mount silencer (sound restricter removed). While the ES might be loud outside the cabin, I found it somewhat infuriating that I could not really hear much of the muffler or engine from the inside.
Removing the recirculation hose added a noticeable release sound on clutch depression. The more aggressively you accelerate, the more noticeable the sound. However, it's not really noticeable unless the radio is turned down or the windows or sunroof are open.
Removing the airbox and adding the cone adds another layer of sound and texture. The overall tone of the engine is lower (mo' betta'!). Also, there is a noticeable intake whrrr? sucking sound through one's teeth? something or other sound on acceleration as well as another hard to describe sound. Again, hard to tell with the radio going.
So, overall nice addition to the aural qualit of the in-cabin experience.
I've never measured the performance, and truthfully don't drive all that hard, so if there is any change I haven't noticed.