What accessories are required to maximise your Link ECU? We sell a variety of sensors and extras which complement aftermarket ECUs. The G4+ KnockBlock is an essential tool for tuning and can aid in the early detection of incorrect ignition timing, lean air/fuel mixtures and mechanical issues. It is used it with ear buds, headphones or noise cancelling ear muffs and features special filtering to allow you to listen in and detect knock early.