Alba took a new z400 to Glamis and tested the crap out of it. From gearing in the sprockets to the full stage 3 kit.
Stock header with slip on really only adds noise in my opinion.
Their kit has been through the dyno and is straight forward.
They give you the right jets for the pipe and air box.
You can alter you pipe and keep the air the same and not mess with jets at all. BUT if you alter the airbox or filter at all, you will need to rejet it. I am no sales person for alba and in fact they have ****ed me off in the past but they do their homework on the kits they offer.
Go to their website and read up on it if you have questions.
http://www.albaaction.com/click on ATV and start reading..
Good luck.. hope you find what you are looking for.