Like the title says, is it going to lean out hardcore passed 3600rpms? And the drill out size is how big? I've got the bookmark for this somewhere but my laptop is junked out. Btw, gx160. No bolt ons as of yet.
With and open header and a K&N style filter 36 thou is about right. You can also change the E tube but in my case the E tube didn't seam to make much if any difference.
Like already suggested by toystory black plug to rich white plug to lean biscuit colour just right