The Gen 1 R53 MINI Cooper S using a rising rate fuel pressure regulator, as the engine sees boost from the supercharger, the fuel pressure increases. This pipe goes from the Inlet Manifold to the Fuel pressure regulator on the fuel rail. Over time the rubber on the end of these pipes becomes brittle and the pipe can fall off either the inlet manifold or the fuel rail, if this happens the engine will run lean due to low fuel pressure when on boost, causing engine failure.
