Nice test Jeff. I've got an 08 STI at the shop that I'll be finishing this week with Cossie heads/cams, Cossie manifold and a .82 GT3076R. I hope to see some larger gains with this combo than you saw. IIRC, your car is running the Cobb SD patch. Wouldn't you expect to see the AFR's lean out a bit if VE was improved by the manifold? Afterall, higher VE would translate to increased airflow for a given boost level. That would lead to an SD fueling car running leaner.