I'm pretty sure it screws to the back of the passenger side head. I need to know what it is. Thanks.

 

Hmmm, lets see.....Its blurry as hell......and oh yea, it definatley screws into something.........or something. No need to thank me,glad I could help!

 

Easter
I think that is the knock sensor and it goes in the valley up toward the front of the block. It sits rite under the water tube that runs full length of the block about 5 inches from the front of the block. It plugs into the wiring harness at the back of the block (passenger side cylinder head)
Hope this helps
Dale