Quote Originally Posted by daveosx View Post
As far as why wire to the block instead of the ECM ?
The cylinder head of either bank is typically less than 2 feet from the O2 bung and the ECM is typically on the inside of the car.

You're hardly doing any extra work for the better wiring. The wire already comes from the ECU to the block. So, just disconnect it from the block and extend it to the O2 sensor.