I downloaded that map, and extracted the files into the base folder, but when I tried to play a different map(Naboo Hills) I couldn't. An error popped up saying something along the lines of "vehicle extension too large". After I deleted the BoC files from the base folder, I could play Naboo Hills just fine. Anyone know why this happened?

there is only a certian amount of different vehicles that JA can support, however, i believe there are a few mods, like ojp, that expand vehicle support.

So should I just switch the maps/vehicles files whenever I want to use a particular map?

yes thats what you have to do

BOC, while a cool concept, has many problems with it, so I wouldn't be surprised if you're experiencing difficulties. Just because a map/mod is popular doesn't necessarily mean it's bug free or doesn't conflict with other popular maps/mods.

This Naboo Hills might be another example (I have yet to try it out, but I downloaded it awhile back).

So, pls explain what u have to do step by step in order to make BoC work pls

I would take out the vehicles that you do not need from base, or use ja plus that has a higher limit of max vehicles and also the 99 vehicle mod, which lets you have 99 vehicles.