WMS Wideband 02 sensor.
$260
The WMS Wideband O2 System is a compact digital instrument capable of accurately measuring air/fuel ratio (AFR), allowing you to monitor your engine and tune it for optimal power and reliability. Leading-edge Bosch technology is used, including a Bosch LSU 4.2 sensor and Bosch calibration chip. Together they provide AFR measuring from 9.65:1 to 20:1 with a 1% accuracy.
This all-in-one control box with LED display is very easy to read and provides real-time monitoring.
http://www.wmsracing.com/o2/index.htm
