The air moving thru the intake manifold and ports is much different than water moving thru a pipe or tube. The water is in contact with all the inside surfaces of the pipe or tube. Air moving thru the ports and head is rarely any closer than .060"-.080" to any of the inside surfaces(roof, floor, walls) as it passes thru, so epoxy filling the cracks is really of no benefit if you are thinking it does anything to enhance flow. Ever see a wind tunnel test where they introduce smoke to show the air turbulence over a car body....wheres the smoke trail....3"-6" inches above the body, not right against it. Same is true inside of a port. Ever have a bug or leaf on your windshield while your going 60 MPH down the road and wonder why it doesn't blow off....
