It does not matter where you look before the ball toss, I receive 160-190km serves all the time. If you are focusing too hard before the toss, you're probably already loss focus when the ball arrives.
The eye and brain knows what's coming and where. You just have to let them work faster by doing the below.
1. Stay fully relaxed and watch the opponent's body language, you will pick up what he will do after 1 set. (Advanced players always do this)
2. Stay very relaxed until he strikes the ball, then you give it all the focus and concentration on the ball only, your eyes will be on the ball only!!!!! your body will move naturally on its own to meet the ball.
3. Lastly, this is absolutely crucial!!! And very very simple. Stay very low and lower your centre of gravity, your eyes will be underneath the ball when the opponent tosses the ball. Your brain process things a lot quicker if the ball is above your line of sight, things like , ball speed, direction and spin. I'm not going to explain the physics of it.
Tennis is easy if you let it be, it's just more physical nowadays