ECU in a Subaru Legacy 1992 ?

[astrocady]

MAF is a O2 sensor too. i should have said "after the front O2 sensor.

MAF is not an O2 Sensor. It is a Mass Air Flow sensor.

Most gasoline engines built after the late 80's have at least one O2 sensor, which is always located in the exhaust. Most cars built after the mid 90s have at least 2 O2 sensors -- one in the exhaust before the catalytic converter (called the front o2 Sensor) and one after the catalytic converter, called the rear O2 sensor.

[ultra_efficient]

the MAF is a o2 sensor, thats why we dont port the HHO before it because it will detect the additional O in the HHO and turn the ECU signal rich then you will start to run rich and waste fuel. come on man we done pass this already! ask anybody, it is a o2 sensor sir. that said, not all cars have 2 o2 sensor, no matter the year ect ect because i have a 2004 Saturn ion now and when i got the ECU pinout to install my VAFC it only had 1 ONE o2 sensor and it was at the front a.k.a the MAF sensor. the back o2 sensor is a.k.a exhaust manifold pressure sensor. please do your research and get your facts straight.