ok when i am adding the extra three wires do i tap into wire that already exist in the ecu pin out?

because i am following a diagram that kataku2k3 made, which looks very good, and all of the places that i thought i was suppose to run new wires from already have wire in them. so am i just splicing into these existing wire.

cliff notes: when adding O2 wires do you splipe into the existing ecu wires?

 

2 of the 4 wires you will tap the existing wire: the 12V+ and the sensor ground will need tapped into the existing wires at the ECU since those wires also provide power to other sensors. The 2 heater wires can be pinned in directly with the old wire removed.