We offer 2 models of sensors, a race and street version both made to work flawlessly with 
your factory or aftermarket PCM. 
 
The standard AC delco sensor is an OEM replacement.
 It will restore lost fuel economy and perform equal to OE. 
 
The rear O2 sensor is a factory O2 sensor (number 12578624)

The race version was designed for aftermarket performance applications
 where *leaded gas is used. *Leaded gas can foul out an OEM sensor 
immediately. This leads to inaccurate reading and poor fuel 
economy. The race O2 sensor, not only resists *lead but outperforms
 the OEM sensor during normal use. It uses an aluminum oxide trap
 layer to keep lead outside the ceramic element through an exclusive 
design. *This helps prevent damage from oxygen occurring when running 
*leaded race gas or leaded additives. More importantly we've tested them
 in our own race cars and know they work very well. Please note that the
use of leaded gas will reduce the life expectancy of the O2 sensor.
 
These are direct plug and play sensors, no cutting or splicing is required.
 They can be used in any 3800 without voiding the factory warranty.
The use of leaded gas or additives is prohibited on vehicles used on 
public roads. Prolonged use of leaded gas will reduce the sensors 
expected life and require it to be changed at a more frequent rate.