99 suburban consuming oil and water

I have a 99 suburban with a 350.  It is burning oil at the rate of about 2quarts every 3k.  Also, I poured a gallon of Antifreeze in the other day.  I haven't really kept track of the water, but I'm guessing that its using a gallon every 7.5 to 10k.  My first thought was a head gasket.  However, someone else mentioned it might be a intake manifold gasket.

Go with your first theory.

the intake manifold gasket is known to leak   i just did mine at 130k