This came from a reliable source. Just so you know, I can not ask for any more data than what is presented below:
2007 - US Retail
Z4 Coupe
M Z4C 355 units
Z4C 3.0SI 409 units
Z4 Roadster
M Z4 1,616 units
Z4 2.5I 6,340 units
Z4 3.0I 3,565 units
Z4 3.0SI 2,503 units
2008 – US Retail
Z4 Coupe
M Z4C 1,013 units
Z4C 3.0SI 1,169 units
Z4 Roadster
M Z4 732 units
Z4 2.5I 4, 680 units
Z4 3.0SI 2, 503 units