GoGo Gas and Fab Fuel are among the few large producers of gasoline in the country. Along with other large producers, they have formed a formal organization to control the output and price of gasoline in that country. What is such an organization called?

This is called a cartel

It's when companies make a decision to influence the market and raise prices for increased profit. This is often illegal but companies keep finding ways to do it by exploiting legislative loopholes that are sometimes even placed there by lobbyists through the parliament.