What the heck are they? Everytime i add a new mod it doesnt work becuase the codes of that mod have these things called pieslices. How can i fix it?

Are you running b26? The things you refer to are a new feature added to Lua in either b25 or b26, I forget.

yes im running b26. and i want the map pack with the city maps and pace and all that. but that wont run either. its always giving me another error.

Pie slices should work fine if you're running B26, so either the mod is broken somehow, or you're not actually running B26.

As for the city maps, it may be a very old map pack and thus recent updates to Cortex Command may have broken the maps. Unless it's Map Pack 3, in which case it should be fine? I'm not sure.

Sounds like you're talking about either Map Pack 3 or an older version of Map Pack. If the latter, get Map Pack 3 instead, it definitely works, I use it a lot.

Also, you've probably covered this already but do other mods or base items with pie slices work? Coalition's grenade launcher should have a pie slice.