[Shotimes] Knock sensor location?

[Jonas Diener]

I've been struggling with a performance problem on my '92 MTX ever 
since I bought it in February.  To try to flush it out I replaced the 
CID, CPS, DIS module, plug well seals, plugs, wires, and HEGOs.

The plugs, wires, and HEGOs each made modest improvements, but didn't fix it.

This summer I drove it from Virginia out to Colorado.  It did OK, but 
lacked power, and I had to downshift a lot.  It got pretty hot on the 
hills too.

On the way back I stopped at a rinkydink gas station in Nebraska 
where the only gas they had was 87 octane.  I had been using 93 up 
until then.  I figured "what the heck, the knock sensor will adjust, 
right?"

So I filled up with it and bam!  It ran like a dream.  Smooth and 
strong the whole way, no more stumbling, no more stalling at low 
RPMs, no more combustion in the cats.

So, this tells me that spark advance is not happening like it ought 
to.  Perhaps the knock sensor is constantly reporting a knock.

My question then becomes: Where is the knock sensor located? 
Autozone quoted me $27 for a new one, which seems reasonable enough. 
Also, is there a way to check the timing with a timing gun?  I took a 
quick look at the crank pulley and didn't see any timing marks...