According to Wikipedia, which is usually fairly accurate, M54s didn't become available until MY2000.
Also, according to Wiki, the M52 in 1999 got Double Vanos (intake and exhaust).
Also, apparently the M54 was only available as a 2.2L not a 2.0L. Wiki indicates that there was a transition from the 2.2L M52 to the 2.2L M54 sometime in 2001.
See the links below for the full story:
http://en.wikipedia.org/wiki/BMW_M54 http://en.wikipedia.org/wiki/BMW_M52
Note: I can't verify this information for truth. So maybe its wrong. But Wiki is usually right.