Get ClientIP Address Behind LoadBalancer

Hi , I have same issue with the client IP addresses. I tested all the ways with BIG IP .I used the iRules methods , also I used the http , fasthttp profiles to retrieve the client IP . The solution works properly , until I deploy for all users and I face a delay in loading the pages more specifically in first login page. In the environment we have more than 10 IIS-2k3 servers which are running the ASP.Net v.2 codes for an application . When I use the http profiles for header insertion methods (iRules or XFF enabling) the system response time increases and the users face the latency. The only method I can deploy with situation is the Standard deployment of the V-servers and in detail I can only use TCP features like fastL4 profiles.

1. I need LB
2. I need client IP
3. The XFF or iRules works

The environment : 192.168.10.x-z >>>>>>BIGIP:192.168.10.Y>>>>>> Other zones of Clients