stock internals, i recommend up to 100hp over stock reliably w/ a good tune for a b or d series. you can get 300whp out of a b16, but daily it won't last as long...even w/ a good tune. i recommend rods/pistons/headstuds for 300 or more. sleeves if really want to push over 500whp consistently, although i've heard of folks pushing 600+ on stock sleeves.