[rotrex]

In Germany we use RON ratings for fuel. MOst stations sell 98 RON (94 US) Octane as the highest, but ARAL/BP sell 102 Octane fuel almost everywhere for 6 cents extra a liter.
102 Octane RON corresponds to a US 98. I use no race fuel. It is just a special pump fuel. Shells offers a 100 Octane, too It is regular pump stuff over here.
Stock timing of this engine naturally aspirated is more in the range of 30 to 32 deg ignition advance.
The ECU I use is a Emerald K3 from the UK connected to a STACK wideband lambda meter.
I run closed loop fueling at all times, even under boost.

I have to look for plug pictures, but they have more of a "tan" compared to yours.
Tried. An AFR of 13 with 0.6 bars of boost. Worked well, but increased thermal load on track.At 0.8 bar running leaner just makes it more prone to knock and I have to pull timing and I lose power.