You'll be disappointed with a b16, I almost gurantee. You'll like it until you ride or drive in something with a B18. You'd have to get into the internals of your B16 pretty to get into the 13's. Even then you'd be pushin it, IMO. To surely be in the 13's you'd have to get a bolt-on kit.

If you want to save some money, and be quicker, go with a B18B and get a turbo kit. Later down the road you cand get a b16 tranny for it if you so desire .