Hi Spinnerrow, check out POWERHOUSE PERFORMANCE, he does some real nice port work, if you look closely at the photos of the work he has done you should be able to get a rough idea of what to do, other than that a good exhaust set up is the quickest way to gain power without screwing up a good engine.
Just a silly thought, have you ever tried using car fuel +/- 20° nitro just to see if that'll make your plane go faster???
I thing the fly boys use 5°-10° but aint to sure on that.[8D]