Theres a thread over on G35driver where a guy put a bunch of CAI's on a dyno with no observable performance improvement, from memory in fact he got the best result from K&N drop in filters.
Having said that, awesome mod btw, looks great, wish I had the skills to fabricate something like that
I am not a fan of the Stillen intake cos you have to cut and modify the penetration from the engine bay. When I buy my CAI wich I probably still will, I'll go with Injen or Tanabe which don't require any cutting