Antifreeze in oil

I need help in figuring out a problem with my 1999 Tahoe. The intake manifold gasket was replaced 1 year ago at 73,000 miles because of an outside leak. Two weeks ago at 91,000 miles I noticed the oil dipstick level was overfull and the antifreeze was low. No visible outside leaks at this time. I took it back to the same repair shop and, after doing a pressure check, this time the diagnosis was a warped intake. The intake was machined, and a new gasket installed. Now a week after this repair it is again using antifreeze and the oil dipstick shows overfull. What could be the problem and what should I be checking to diagnose and repair this?????

take it back and tell them to fix it again. or get a new intake.

Is it possible the leak is the head gasket? I would imagine the possibility exists that antifreeze could get in through a oil galley in the head. Just a thought. Could also be a cracked cylinder wall or anywhere there is a coolant passage that would exit to the crankcase(hopefully not!)

head gasket