First of all have you tried using a higher octane fuel? That will isolate whether itis "real" detonation or a problem with your vehicle. Go for a couple of tankfulls of the highest octane fuel you can find and see if it still happens. Go to a different supplier too as some less scrupulous ones "water down" the fuel with other volatiles, decreasing the octane rating.

Assuming it hasn't


Having obviously changed everything else and other sensors are not throwing codes, I'm going to go out on a limb here and say it is likely to be an electrical issue, either with the wire from the knock sensor to the ECU, or internally within the ECU.

Axeman should be able to give us a bit of a clue as to what pin the knock sensor goes to on the ECU and if there are any splices within the loom (known problem in other areas). Make a lead up that connects the knock sensor to the correct wire to the connector in the back of the ECU. Don't cut the old wire, just use a 20 cent wire joiner - plastic thingys with a cover that clips over the top of them. Drive around and see if that fixes the problem.

Next solution by default would be the ECU, either causing the detonation through timing issues ("real" detonation), permanantly locked into "limp home" mode for some reason (internal failure - code??? causing fixed timing, when mixed with low octane fuel may cause detonation under moderate to heavy load), or not sensing knock sensor (faulty preprocessing stage of ECU). I don't know if the ECU's are swapable between years, but if you could get your hands on a spare from a breaker for a loan you could try swapping them over (this could be done in the breakers yard if they want to give you any grief about it, might need someone with a code reader too, to clear old codes).

Not much else that comes to mind, given that you appear to have jacked up the stoplamps, and changed everything else.