Get a new knock sensor, intake gasket set, and a knock sensor harness. You have either a bad sensor or harness, and the ecu is pullin' timing.
Z1 has the harness.

 

Good advice about the harness. I ordered mine from a dealer out in AZ who was selling them for $67. You'll get the fuel injection harness along with this harness. I'm not aware of anyone who sells an OE stand-alone harness for just the KS.

There are some good write-ups on here about tearing into the upper engine block...like you'll need to do to replace the KS. Just a few pointers, from my recent experience...1. you'll need to take the intake manifold off of the car to access this KS (not to be confused with the upper/lower plenum), 2. buy new gaskets, as the OE gaskets have a black factory sealant on them that shreds when you remove the parts, 3. budget at least half a day for labor--you will need to clean off a lot of crusty, oily varnish and goo. It would be foolish to not clean all this gunk out while you have it disassembled. 4. Replace the fuel injector O-rings while you have the chance--cheap insurance and you have to take them out anyway. 5. I've read about people spending hours fiddling with the KS harness connector on the back of the engine--yes, it is out of sight. No, it isn't hard to disconnect. Since I had a new harness...I cut the old harness and left the old connector in its metal tab. The replacement harnesses are slightly shorter and will not fit in the tab anyway.

On a side note, if anyone else is getting a stored KS code P0327--also called a "ghost code" by some--you will not get a lit MIL for that code. I was scanning my ECU because of a loss of power and rich running condition (which resulted in carbon residue buildup on my bumper) when I pulled it. I don't understand why the engineers at Nissan/Infiniti would do this...but this code can easily fly under the radar of most drivers who don't pay attention to things.

Sorry I don't have any pics...I had to get this all done quickly to avoid wife aggro. You married guys know what I'm talking about! Hope this helps.

ps--Two things: 1. people have mentioned the car acting completely different after you replace these parts. They are totally correct. Its like my car was asleep before I fixed this code, now it is awake and full of life. Night and day difference! And 2. people have posted that the KS rarely goes bad--my G has over 120k on it and when I tested the old KS, it was within factory spec (568k Ohms, I think). I replaced it anyway--$30 for an OE part is more cheap insurance. Oh, and the Import Direct brand you can get at O'Reilly's is exactly the same as the factory part--down to the manufacturer, serial number, markings, etc.--it was made in Japan. Cheers.