SNAT Issue with two virtual servers

as long as you have floating IP(s) configured on that egress vlan, that should get you going.

https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm_configuration_guide_10_1/ltm_snat.html

When automatically choosing a self IP address to map to the specified original IP address, the system gives preference to floating self IP addresses over static (non-floating) self IP addresses. This prevents any interruption in service when failover occurs. Note that if no floating self IP address is currently assigned to the egress VLAN, the system uses the floating IP address of a non-egress VLAN instead.