Was it holding 12psi from 2000-6000?
As the others have suggested, check the usual things - Split DV, leaking boost pipe O rings etc, update the PCV to the latest one etc. There is nothing complicated about these engines. All of the common post turbo boost related issues are cheap and easy to fix.
A bad MAF will usually show up at idle but your idle g/s reading is in the right ball park. MAF will reduce as the load on the engine reduces, so we need to see some logs to analyse. Log - MAF, Lambda, Lambda regulator, requested and actual boost pressure, requested and actual fuel rail pressure, ignition advance and the knock regulator.