Still have mine in the closet unbuilt...

Same here, I've been to lazy to go get this shielded cable and knock sensor I need.

I wasn't that impressed so far. Sounded kinda flat to me. The guy on the video made it seem like you could hear "everything".
Changes to make:
-- best shielded cable I can find
-- try changing from Bosch knock sensor to the Miata OE sensor
-- check into something called a "contact microphone"
I have other projects I'm trying to finish before I get back to this.
Cheers,
--JB

The Miata one is garbage. I think it's the one you are using though.
I forget if he gave a part number for the one he used.