Vehicles fitted with Electronic Fuel Injection (EFI) from the factory have what is called a surge tank or swirl pot in the fuel tank - so when you're accelerating or cornering, fuel can't rush away from the fuel pickup, causing the engine to stall or surge. A surge tank is necessary when fitting EFI to non EFI vehicles. The surge tank acts in the same manner as a swirl pot, supplying an even flow of fuel to the injectors.