Its Kongo Central not Congo Central. Its with K to make a difference with Congo since that's directed to the Kongo ethnicity and Kongo Central being middle between Congo Brazzaville and Angola where also people from the Kongo ethnicity live and the three countries being part of the historical kingdom Kongo before it got splitted in three countries by Europeans.
If it was Congo with C, than it had to be in Kasai since that its in the centre of our country.