disable SNAT on a forwarding virtual server

Hi,

 

 

My setup is a little bit strange. Our developers have placed some servers behind the LTM (their default routes point to the internal floating IP) but they are not being load-balanced nor a they a part of a pool. We recently created a forwarding virtual server to allow them to ping abother server outside of the LTM (external vlan). The problem now, is that the same server for which they are pinging is attempting to initiate communcations back to them and they are SNAT'd. How can I disable able the SNAT address for only those particular servers and only when they are contacted by the one server on the external side? What would the irule look like and where should it be attached? I thought about using the server_connected command but didn't know where to put it. Any help is greatl appreciated.