Sorry to call you out to Dave, but there seems to be alot of boxster owners here that don't have a clue. You say you make 221hp with an evo kit? I assume you mean the air intake that evo makes for the car. If you have the intake, and only the intake, your car would have gained possibly 5hp at the rear wheels. 2.5L boxsters like yours have 201hp at the crank which gives you approx 175hp at the wheels. With that super evo intake you put on you maybe have 180hp so please show us a dyno sheet of your 2.5L that has box S power and I will shutup (;
Cheers.