I remember there used to be a file in previous versions that held a list of teams and the stadiums they played their home games at.

I noticed Juve doesn't play at Della Alpi in manager mode - I'd love to edit that. EA can be so lame at times....

Juventus doesn't play in Delle Alpi anymore, they moved to the Communale Gran Torino for this and possibly the next seasons.

Problem solved!

Honestly, if you still want to change stadiums, open the fifa.db, click on "stadiums", look for Delle Alpi, see the number next to it, then click on "teams", forth or fifth column is called "stadiumid". Replace the number with the number of Delle Alpi you memorized. Ta-dah! That's all.