I see you are using those custom intake manifold bolts. They come in the long version 2"" and the shorter version 1 1/2".
I would drain down 2 gallons of coolant out of the system, then remove the 4 outter corner intake bolts and put in shorter ones. You custom bolts may be too long and are bottoming out in the bottom of the threads? Hence not pulling down the intake tight enough so it is leaking on all 4 corners.
It has got to be something like this if it is leaking on all 4 corners. Pull out one of those corner bolts and see if the end of the threads are starting to burr over from bottoming out.
4 shorter bolts beats pulling the intake all over again.
