Bill,
220 to 227, is about 10% more power. The piece of information that is missing is what was installed on that particular aircraft before this airbox change. I saw a 5 kt increase going from a really bad filter arrangement (high loss, no ram) to a really good one (low loss with ram). 3% is quite a bit, so test conditions might be a bit suspect.
Chris Zavatson
N91CZ
360std