Exhaust plug only. Required when you install a custom exhaust system in combination with a high flow or otherwise custom air cleaner kit. The exhaust plug (981567) is used to plug-off the stock wiring that runs to the mechanical actuator valve in the stock exhaust header, and will prevent trouble code triggering by the stock ECU. For the air cleaner the other plug (981570) is used to plug-off the stock wiring that connects to the sealed-off intake valve actuator (OEM 70991-07) located in the stock air cleaner housing of late H-D models. Again, this also will also prevent trouble code triggering by the stock ECU. Used on H-D models, equipped with a mechanical actuator valve inside the exhaust only. Note: See 981570 for the Dynojet air cleaner plug only.