I had this on my Optima. I loved the sound it gave, and there may have been a bit more HP. I am looking to get rid of this kit (Filter only has about 8k miles though it) since I have recently sold my Optima.
I just installed an HPS intake system on my 2013 SX T. Feels a bit more responsive when you hit the gas hard, and you can definitely hear the turbo spooling up as you accelerate. Nothing too crazy that will blow your tires off your car, but still a fun bolt on mod. I'm happy with it.
I'm running the AEM on my '16 SX-T and love it. The sound is the most noticable thing to me since adding it however I hadn't dyno'd my car prior/post so its hard to tell what type of true hp gains I'm getting.
Also installed (pretty close together in timing) most of the other performance enhancing parts from the K5 store (Kinetic exhaust, Lap3 Performance Tune, throttlebody spacer, oil catch can, BOV). All of that combined with the AEM gives my car a noticeable improvement off the line and while driving vs pre any of that.
Sorry for the novel, but I'd recommend it and its super easy to install/uninstall.