Plug, Secondary Port Throttle Delete, for 90~95 ZR-1 LT5. Sold by the set of 8 only. Eight (8) drive plugs are required per engine.

The Secondary Port Throttle System (SPT) is activated by the "Valet Key" and enables the ZR-1 LT5 engine to develop full power by enabling the Secondary Port Throttles to open the valves in the runners & activate the secondary fuel injector in each cylinder.  The system is an elaborate array of vacuum hoses, check valves, actuators, and linkage. 

The system is normally very reliable while the components viable, but age has taken its tool, and the result is frequently vacuum leaks & poor function.  Experienced LT5 builder/tuners have now had years of experience with deletion of the system and can modify the Prom calibration to eliminate the need for the SPT.  Driveability is the same and full power is seamless & on demand at all times.  The modification is easily reversed and does not alter the appearance of the engine.