I was considering the G3 but found, after looking at the dyno chart on the Stillen site, that the majority of the gain is between 6500-7200 rpm. The mid range is significantly less gain. I don't drive much at the redline so I didn't think that a 2-4% hp gain in the midrange rpm's was worth the install, maint. and $600. You can check out the chart at the Stillen site.
http://blog.stillen.com/wp-content/g...yno_402852.jpg
I have the Stillen CBE and love it. Nice resonate tone, kind of like a stock G37 sound on steroids with no drone at all. Butt dyno says the power is improved.
Stillen is a class company and makes great products so I would go with the G3 if you think the power is desirable for your driving style.