Hello dear
Congratulations on your score and getting a call for WAT and PI.  For getting selected in SLAT all of the three are taken into consideration than they make a merit list . Since you did well on your WAT but you say your PI didn't go that well as expected. I could only say that you have to be patient enough and wait for the results and have hope let's not be negative regarding the selection. May be it's just your thinky that you did do well as per you thought but in reality they might have liked you and you might actually have chance of getting into SLAT. So just keep your fingers crossed.
Best of luck for your future endeavours.