Sounds like a big vacuum leak possibly, and the MAF is not switching the C/O relay for the fuel pump because it's not seeing much airflow. If you hold the throttle down a bit, will it stay running? Did the air inlet tube get a crack in it, past the MAF? Possibly a huge leak from the manifold gasket, but it seems it would still run if that were the case.

The engine sounds great though! As Tim stated, no knocks or strange sounds.