FYI

Just instrumented my '05 STI with a Horiba MEXA-110 AFR monitor. Car is stock except for 3" TBE. Sensor is located ~2" post turbo (catless Helix downpipe). WOT AFR is 10.4-10.8:1 throughout the 3-7k RPM range. Very smooth and stable. Excellent transitional fueling. I am very pleased with the numbers and would not change a thing. Running California 91 oct. fuel.

from the map notes:

"Target A/F Ratios are mid 12's under load before the onset of boost. Under full load by 3500 RPM the A/F Ratio will drop to mid 11:1 and gradually run richer as RPM's increase ending at high 10:1 A/F at redline."