Have I mentioned I like factory FPRs. I have yet to see an aftermarket FPR that is stable.

Nothing looks wrong with the fuel map.

I would try adding some timing where the engine feels week. Go up 2* over a test area and drive it. When you feel you are near a limit, either push a test say a small area up 3* to force knock but then start backing off 1* to make it safer. If knock was not detected in a test area raise the surrounding bins and test again. Sooner or later you will get into the knock circuit, or detect it yourself.
Knock will probably be around 17-1800 Rpm and 3-3300.

When you get around to an exhaust the Aussies have headers for these but if staying with iron then use the original Y pipe but go to 2 1/2 back from the original joint where the two sides meet.