Where did you get your -15% global from anyway? You're running 8.55:1 AFR assuming 600cc.
I'd bump it to -25% then go slowly from there. This will be from 9.5:1 - 9.8:1 with the estimating due to injector flow. -30% is 10:1 - 10.5:1. That wouldn't be so bad either to just stay at. Turn the boost down to maybe 18psi, set fuel to -25 or -30 and start re tuning with the boost watching for knock. Hope your airflow skyrockets.