The only thing people here buy from Stillen are thigns liek body kits. Do you think there is a reason that everyoen who has replied says 18rwhp from ehaders is not goign to happen? Do you think the people on this site dont know what they are talkinga bout? And how is it that when you ask a question about headers that you clearly know nothing about, you seem to so adamantly disagree with the answers people proviede you?
Why dont you ask the vendors on site what they think of the hp gains? I highly doubt they will tell you 18rwhp on an NA.