Hi Kunal -
How are you determining that the wrong user is being used to execute the viz?
Please explain what SSO mechanism you were using, and exactly how you turned it off.
To begin with, get rid of the &:iid=1 on your vizpool string. By leaving it on you are forcing Tableau to use a specific vizql session. I see you are also using :refresh - this forces Tableau Server to requery the datasource each time the viz is executed, which it generally doesn't do in the real world. In the real world, the Server will rely on cache when it can...So unless you have a specific reason why you want to hit the database each time a viz renders, you should remove this string as well.