The reason you sometimes see better number on the dyno is because that engine is still pulling some timing out because of the amount of knock. It's still hearing something so it's still being cautious. This is especially true with most Japanese manufactures because in Japan they have either 96 or 98 at the pumps so that's basically what the engine is designed for. Those gains are also usually seen on more modified engines as well that have higher compression with upgraded internals or with forced induction. Basically, the more resistant and engine is to knock, the aggressive you can be with advancing the ignition (which the ECU will try) and more boost. Seeya.