Had the itnermix problem on my 2000 C4 Cab last September, basically sat all winter. Started removing the engine 2 weeks ago and tearing it down last week. Found the source fo the problem and here it is.

The crack is at Cylinder #1, at the inner exhaust valve. Reseach shows that cracks usually show at either #1 or #6 (which are essentially the same location in the head casting) at the exhaust valve. Hope to be back on the road in a few weeks.

 

there ya go! you gotta drive the dang thing -------don't let her sit or she will get mad at you......