The mod I've done is very simple.
I've only done one mod -- the "harakiri" mod (Japanese Seppuku reference). This involves poking a thin needle into the bass port, puncturing a film that is just below the shell surface. Once the needle penetrates the thin film, you'll feel it and you can stop there. If you go further, you risk hitting the driver as well. It's really not that hard to do, it's easy to go slow and stop right after you break the film.
This mod decreases the bass. Stock tuning, these are pretty bassy and definitely a good bit above neutral. Opening a small hole in the film lets air to escape the back of the housing, which will result in more neutral/natural bass levels.
Another mod, which I have not done, is removing the filter from the iem. You just lift the silver plate on the nozzle, and underneath there's a foam (HifiMan) filter. Just remove it and put the silver grill back on.
This makes them more treble forward. I prefer to avoid sibilance or shoutiness so I left this alone.
There's also another mod which involves venting the actual tip... didn't bother to do that because it seems complicated, but the user said
after he did all of these mods, they're so good that he's selling his Andromeda.
If you're interested in reading more discussion about the TFZ 5 you can search up "tfz endgame" on google