Basically, any gains less than 10 hp, or really even less than ten percent, are pretty hard to judge on a dyno. Take it all with a grain of salt.
Sorry I got to this party so late though--looks like it was a fun discussion. I've spent a lot of time discussing butt-dyno gains online with people in the past.
BM: Don't know if it's already been said but if you want to see real gains the first step would be to get an exhaust and intake upgrade, THEN tune the ECU. Tuning the ECU by itself won't do anything worthwhile for you.
Also, if you're wishing for more power out of your Boxster, I'd recommend selling your 987 and just buying a 987S instead. That would be the most cost-effective way, honestly.