I have done the EU2 tune on my '03 530i with same engine. I did it because my car has 400k miles and I was getting cat inefficiency codes.

Car runs well with EU2 tune, at least as good as before. Not sure it's better.

I think I will pass emissions, but am not sure. My sticker is not due until Feb '21.
In my state, pre-'04 cars do not need "readiness" monitors to be on.

I have lost the check engine (SES) light..It does not go on even when I turn the key on.

I just check for codes every couple of weeks or so.

Thoughts-
If you are going to the trouble of patching the bung, it shouldn't be much more work to repair the bung.

Also if you do flash to the EU2 tune and don't like it, you can flash back.