The numbers are 22Mbps for Restricted models and 63Mbps for Unrestricted/Failover models, which use the VAC+. However, you shouldn't expect to achieve those since the measurements are done while the Pix is doing nothing else and processing full size packets.
The complexity of the configuration (dynamic remote clients or static lan-to-lan), number of concurrent clients, per-user ACLs, and other items are usually more of a concern than pure throughput unless you have a really fat Internet pipe or are performing encryption on FastEthernet connected speeds.
