F5 VE with VMWare problem

No nowhere else to enable (except iRule actually).

Either your network topology is slightly different in prod or - you mentioned a firewall rule blocking the request when it had source IP of the client. Perhaps if you change the rule to allow client ip and self-ip through to the server, you can take snat off and see if it still works. So the point of difference between environments may be the firewall rather than the F5.