Save you hard earned cash. Honda did a great job squeezing every last HP out of that motor as-is. None of the "bolt ons", nor the PV3 add any noticeable HP and you will just be throwing your money down the drain. Save your $$$ for internal engine mods or a turbo.
Take it from someone that has already spent the money and time for you. $2,000 in experiments and I might have gained 4 HP. $500/HP is not worth it. My machine is almost completely back to stock except I use the PV3 to lower the cooling fan engagement temp and raised the max RPM a little.
Search and you will find a rather lengthy set of posts (or should I call them Rants) from me about this exact subject.