@ciane
So I did this - "Make a new folder in your Sims 3 Saves folder called IPonlyRdy.sims3 and copy these four files into it: https://www.mediafire.com/folder/hh78ai99s6a1y/IPonlyRdy"
After doing this, I entered the game and there was no lag, but whenever I tried to save I got Error 16. So I quit and noticed that TravelDB.package had moved into the CurrentGame.sims3 folder. I figured that I had accidentally put it there, so I removed it and tried again, being extra careful this time that the files go in the right place. When I loaded up the game, the same thing happened. And when I quit, TravelDB.package had moved into the CurrentGames.sims3 folder again, and this time I'm 100% certain I didn't put it there by accident. It seems it is moving there by itself.