No kidding , the restriction is the fitting and drain, I was looking at 30 degree push loks and the -10 AN billet drain fitting, not the 1/2" pipe thread.The flow will only be as good as the smallest orifice. With a -8 on bottom of turbo and a -8 on the block, putting a -10 line between them is not gonna help.
All was well until the T66 pushed its way into things, now the factory line leaks. and yes the block is 1/2" MPT, just remove the brass adapter.