For model year 1999 Mirage became 9-speed and Avanti stayed 8-speed but got a makeover.
The derailleur range was:
* New for model year 1999
From 1999 the '9' in the second part of the model code indicated 9 speed, and '8' in the second part of the model code indicated 8 speed.
These images come from a pdf downloaded from the Campagnolo web site some years ago. The larger text displays in a plain sans-serif font rather than the more decorative typeface used on the print version. The rear derailleurs are featured from page 24 to page 30.