I think the twist throttle kits you adjust idle by the throttle not idle screws, thats how my cousins blaster is gosh i hate those twist throttles. i could be wrong, tors delete kit would be first mod if i had stockers.
anyways, yes a 27.5 pilot should be good for that temp. make sure its a genuine mikuni jet, you can post a pic in here we can tell you. shouldnt be too hard to tune 27.5 pilot 300-310 main should be good for your mods and 30-50 degree temp