I couldn't see it in the pic, and from where he circled, I do not think that is exactly it, but it is right near there.
Does your alternator have the alternator cooling duct on it? If not, you need one. If so, it is right behind that. You will need to remove the duct in order to see it. If not, get one, well it is below the rear exahust manifold a couple of inches.
The knock sensor is pretty identiable, it should eb a brash colored cylinder, about 1/2" tall, with a hex head and an electrical plug on top of it. It screws in and out. The electrical plug is not standard and be careful not to break it. It is shaped like an oval. To remove it, push the two wide ends of the oval together, forcing it to look like a circle. Then gently rock it back and forth and pull it. To install it, just push it on.
Hope this helps!
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1992 Lumina Z34 5-speed For Sale
14.78 @ 92.68
1992 Lumina Z34 5-speed For Sale
Offered to donated its organs to Fiero