Have you dynoed your 2.7L Boxster?

You can look at it this way too:

1) Your increased HP (11) cost about $181 per horse ($2,000/11).

2) Comparing a 2007 987 vs. 987S the HP increase is 50 and costs $9,900 or $198 per horse. A 2006 comparison would be $242.50.

Looks like you did OK. The most important thing is that you are happy. And that has far greater value than anything!