Get a valve job, and set your timing correctly.

Aprx. cost? 300 bucks total. May I also suggest while you have the head in the shop, give it a decent port & pollish? Ive been _told_ of 40hp gains from just that alone on SOHC honda's.
(Ramsey's in Tampa). They also take a week to do it. *Shrug* - Most shops however, only take a day.