The electronic fuel injection system found on Nissan Z engine powered vehicles has been adapted to work in 510s with both Z series and L series engines. It is a mass flow system, which means that a "flapper door" air flow meter is used to measure intake air volume and temperature.
When used on an L-series motor, an injection intake manifold must be either fabricated or aquired from a non-US vehicle as fuel injected L engines were never sold for US domestic consumption. However, many JDM efi manifolds found their way to the US attached to imported L18 engines in the early 80's. The import manifold can still be found for sale.