Engine performance

Good evening.My name is Asier and im new menber and this is my first write.I dont know if is this the correct site to make this questions but im going to try.We are building a s1000 rr engine full performanced and we have got an important dilemma with the cylinder head performance.I reed on some forums that are people like Bob Carpenter or kwsmotorsport (engine builders) who make head porting on the s1000rr and get power. In the other side is Alpha racing (bmw official builder) who said that the s1000rr even the OEM have too large exhaust and admision holes and they use on the WSBK races, reduced holes heads.Like you see, here are two different opinions.If any of you have information on this, i would ve very gratefull.
Thank you so much.