That is part of the recall that Ford put on the Focus...2000 and 2001 Focus have electrical issues...I'd go to the dealership and get them to check if the recalls have been done.
If not, it doesn't matter if the car is out of warranty or if it's been souped up...they'll fix it for free.
But honestly, you're best to get rid of it and if you like the Focus and tuning them up, buy a used '02 or '03 model with the Zetec engine. More initial power, fail-safe cooling system, and no recalls at all.
You'll have better success with it.