Excellent...I'm not sure if you get any added hp with just PSE; I know with the different intake you do for sure. I just wish they would make PSE a cheaper option...without it on a stock Carrera, the sound is just too muffled. I've heard this is because of Swiss noise requirements.

 

I remember reading somewhere that PSE is included w/ X51 because the exhaust is more free flowing, and if someone wants to install the power kit not from the factory, pse or an aftermarket exhaust is recommended to match the added dual air intake. I'm not sure if this is fact just remember reading it somewhere...