XFF AWAF

Hi noplonik , 
Check 3 scopes of Configuration used to add this feature : 
1) Check the attached { http } Profile and opent it from Profiles sections , and disable "XFF" Feature , you will see it easly in http profile settings , but make sure you are selecting the http profile which attached to the required virtual server { Which contains AWAF policy }. 

2) Check if you are attaching an iRule in this Virtual server {  Which contains AWAF policy } used to insert XFF header in HTTP requests, and see if you can delete it.

3) Check if you are attaching a LTM policy  in this Virtual server {  Which contains AWAF policy } used to insert XFF header in HTTP requests , and see if you can delete it.