I am not sure what a 99 Saab supports but as far as an OBD II CAN interface goes take a look at what we offer at
www.obdpros.com this one is one of the most reasonably priced interface and offers a slew of additional commands such as the ability to monitor the can bus and keep up with the full 500 KBit traffic with PC side speeds of upto 1.25 Mbits.
Are you in the US? I can check out the schematics for the Saab and let you know where the I bus and Pbus signals might be available
Thanks
Paul