hate to say it but I remember talking to you about this 2 months ago and I had the same sound... that motor is dead now and it was from a main bearing and then, a rod bearing. I know you feel like it is something else, I have listened to you mpeg and mine sounded VERRRRRRRY similar... I also had a B18C1

holy crap, I read your post again and my sound was resonating
from the same place under the intake manifold. bro, stop this and pull the motor, tear down the bearings again and start over. It sounds like a crank bearing