AEM�s 4-Channel Wideband Air/Fuel UEGO Controller (PN#30-2340) allows users to simultaneously monitor individual cylinder Air/Fuel Ratios (AFR) on up to four cylinders, and can monitor up to 8 individual cylinders with the addition of a second unit (up to 16 cylinders with four controllers). The AEM 4-Channel Wideband Air/Fuel UEGO Controller can increase both engine performance and reliability. It is the most affordable multi-channel air/fuel controller available, and is a must for anyone using an engine management system or data logger to monitor and/or tune individual cylinder AFR.