400ex sprocket ratio question

Hey i have a 400ex with a fmf powercore 4 and a k&n airfilter with jets. I was wundering what the best sprocket combination would be to race on a track against other 400's. My rear tires are 18 inches and the front are stock. I am currently running a 16 front and a 36 rear. I have a 15 and 16 front to choose from and a 38 and 36. Out of the sprockets i have, i was wundering which combination would be the best for coming out of corners and jumping but still have a decent top speed.

Thanks.