eh..and the fact that the pre-obd distributors always throw codes and the obd1 distributors interchange better with obd1 and obd2 distributors. Multitude of obd1 ecus that can be modified to meet many different setups. One 4-wire O2 sensor mounted in the traditional location typically found on many exhaust and test pipes as opposed to the two 1-wire O2 sensors found on the exhaust manifold. Quit a few reasons.