Perfectlap,
Attached are dyno charts from Evolution MotorSports for the Air intake and Chip/Intake upgrade. I did several months of research and inquired with a number of Boxster owners who did the Air intake before putting down the $400.
According to the charts, there is actually 11hp increase to the wheel with just the the air intake. I guess we can also argue that the dyno's are fake and it's all B.S. since it's Evo who makes the intake.
Also, check previous thread
http://986forum.com/forums/showthread.php?t=4431&highlight=chip. He dyno 246hp to the wheel (almost 280hp) after headers, chip and air intake.
Aside from numbers, I think what really matters is how it feels. As long as it makes me smile a little more driving the car, it doesn't matter if it actually adds 2hp or 20hp.
I agree with most Boxster owners that the car is great as is, but a little icing on a great cake always makes it taste a little better.
With regards to the tires, I didn't mean to offend your opinion. I was referring to R compound tires as an upgrade.
P.S. I didn't mean to stick all the numbers at you, but I can't help myself since I'm an Accountant and I use to be an auditor!