411 REFERENCE · Wikibooks
Nissan 240SX Performance Modification/Ignition and Fuel Management/Piggyback Computers
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
A piggy back EMS system intercepts the signals from the load sensors, modifies them, then inputs them into the ECU. This can be an effective way to tune your engine.