im in the middle of swaping parts from the b18a onto the b20z and i came across a little green sensor looking thing on the back of the b18 which isnt on the back of the b20. Its just to the left of the oil filter. What is it, and are there any changes I need to make when hooking everything up? Thanks.

 

if its the one on the water neck then you have to make it to fit the thermo housing of the b20z i believe and that green connecter is the fan switch

 

are you talking about the "knock sensor"?

 

b18a don't have knock sensors