The airbox mod worked nicely for the previous generation Z1000's.
Here's an excerpt from the Project Z1000 that Motorcycle-USA featured:
"To better allow the 953cc inline-Four to inhale, White Brothers' R&D guru Gary Jones came up with the idea of making a hole through the Z's restrictive stock airbox cover. Jones, one of America's first motocross legends, cleverly heated up a metal cylinder of the hole diameter we wanted, then set it atop the plastic airbox lid to melt a perfectly shaped opening. This simple modification is highly recommended, especially when using an aftermarket exhaust, as it gave us a clear advantage from 4000 rpm until redline, plus an additional 4 horsepower up top, now to 129.3."
Link:
http://www.motorcycle-usa.com/372/11...00-Part-3.aspx