I am quite content with carbonio. I don't have any dyno runs to back up my feeling, so it could be the placebo effect. I didn't get the carbonio till after I went stage 2. Rocked the stock intake for about a thousand miles then switched. Throttle response is improved and above 4k the car feels stronger, unless my clutch slips. No clutch slipping with the stock airbox, have minor slippage with the carbonio.
Just want to add that I ran the car on factory tune with intake and downpipe for a few hundred miles and that is how the car should have been stock. People say stage 1, but I believe it's too peaky for the average driver, but the intake and downpipe give good throttle response and smooth power. Very nice delivery
Also want to add that I'm not a carbonio fan boy, and would have went in a different direction if I wasn't planning doing a k04 install in the spring. I say buy the intake that the tuner uses to develop their tunes. My $0.02.