could just be mechanical noise you're picking up, usually from my personal experience most knock occurs where peak torque is reached, unless timing up top is pretty strong and there could be a chance it's knocking there too.
I just did
Your VCT is enabled all the way to redline, perhaps try only setting at 100% between 1500rpm & 5000rpm (as a test). Of course doing 2x runs and finding the intersection point is more ideal - but I'll leave that up your tuner to decide on.
I wasn't a fan of them at all, for the price + a little more some Nitto INVO tyres are a much better option or even Kumho KU31 (not as good as the Nitto).
is your car oversteering with some power down OR as you turn in hard and coasting?
The factory VLSD is rubbish and often single spins so as you enter a corner (on a track that is) and apply some moderate power down the rear end ends up kicking out thus delivering some sideways action.
I found the best mod I did was install a proper mechanical LSD, there's some understeer on power now however so much more controllable compared to before.
there's a decel timing advance table in Nistune, don't worry about it too much.. you could lower those numbers to induce a pop and/or flame on decel too
That 350Z conversion is interesting, hopefully there will be a full off the shelf kit one day - seems there's still some mucking around to get it to fit.
Would love a 6 speed in my R33!
stock fan with a decent radiator works tits, those GK Tech fans are hideous - pointless mod, I removed two of them off 2x S15s that were overheating on the track.
You want it to come on quicker and harder? Get VCT going like others have mentioned.
It's day/night difference in terms of low down torque and response.
If your tuner doesn't think so, then it's time to find a new one.