I'm losing about 3/4 gallon of antifreeze in a 2004 Chevy 1500 5.3

Its not leaking anywhere! It obviously is burning it! They initialy said hopefully the intake manifold gasket...now they are saying that it doesnt run coolant through the intake manifold and that it is most likely the head gaskets!

It has 90,000 miles and I am hoping like hell its not head gaskets...but Im sure it is.

They are pressure testing coolant and its holding good pressure and its NOT going into the oil!