So what is this thing, and what does it do? As we all know, your air and fuel ratio are a great measure of  how efficient your tune is through out the RPM range. It is important to monitor while tuning, and under certain circumstances it is advantageous to monitor during vehicle operation. AEM has created what is essentially a wide band sensor perfect for tuning without the need of a gauge. How does it work if there are no gauges? The AEM Inline Wideband UEGO Controller has outputs for datacontrollers and pretty much every engine management system currently available. The controller use a Bosch sensor accurate to 0.1 AFR, and reads Gasoline, E85, Ethanol, and Methanol.

[source: titan motorsports]