What is the AI for?

Your balls shrink when you're on juice because they're not getting enough LH.

The whole point of taking hCG is that when it reaches your balls, it does the same job as LH, so it stops your balls from shrinking.

Where does the AI come into it?

By the way I don't think Tamoxifen (or Nolvadex as you call it) would do me any good because I hear it acts specifically on breast tissue.