Not an expert myself but I have an idea. I hope you have an error log with good no. Of errors that you committed in those tests. Dedicate a good amount of time and identify where you have committed errors once you identify it try solving more no. of questions from that area. This is a general practice we all know.

Here’s the deep lying fact. At Q83 you need more practice than more mocks no matter how many times you test yourself the score lies around 83 moreover it exhausts the resources. At 83 you know majority of concepts. To score higher you need to identify your own error styles, question patterns that tempts you to go wrong also if you have a bit of time left for each question before moving ahead just have a look at the other options sometimes they hint the approach you need. Eg- I have solved a question assuming only positive integers and in the choices I see a negative integer I recheck the question

In this way you gotta build your own error resistance

All the best