Bypass the origin Client Source IP to Back end Server instated of floating IP

Since Auto Map means you will automatically SNAT traffic to your floating self ip, the obvious answer is to disable the Auto Map and change it to None. Now requests to the node are made with the original client ip address that connects to the BIGIP.

However if this a HTTP application it is common that they look at HTTP headers to get the clients IP address. The easiest way would then be to using a BIGIP HTTP profile enable sending the HTTP header "X-Forwarded-For", which will contain the clients IP address. The HTTP server can then look at this header and determine the client ip address.

You can also add custom HTTP headers using an iRule. If it is not an HTTP application, you can use the first suggestion, or iRules to make a more granular policy so that not all connections are using SNAT etc.