actually I was trying to figure out the same thing. There is a thread on here (see link below) that has dyno'd his car before and is going to do it after to see the HP increase. Some people think Porsche purposely restricted the boxster's air flow to cut down on HP to make the 911 look faster. I am eager to see the out come
http://www.987forum.com/forums/showthread.php?t=21061
My philosophy is a few HP here and a few Hp increase there start to add up!! *(as long as its cost effective)