Vegas,
Yeah this is possible all you need to do is
change the internal gear on the ergo levers (STI is
shimaNo).
There are detailed instructions at
CAMPY ONLY
further instruction are at:
upgrade your ergo levers
and for required parts:
Branford Bike
They detail what you will need to convert from 8spd to 9spd
(or even 10spd).
Hope this helps,
Marty