I realize that it will be hard to do (restore a bit of faith in GM's engineering), but here is a bit of info on this particular engine, found in the Impala.
We had one of these apart the other day, it bent a rod due to being driven thru a large body of water (we had some sort of flash flood the other day in our city). Engine ingested water and bent the rod.
This is the code N 3500 engine, which uses the variable valve timing (on a camshaft in block design, no less!). While it was apart, we noticed that GM has completely changed the design of the cooling system. The intake is dry, there are "no" cooling ports in the cylinder heads, and they have moved to an external water crossover system that is the same design that the Northstar has used for years.
No more intake related problems on this engine. At least as far as coolant getting into the oil. I took a couple of pictures of the intake gasket and head gasket. Just for interests sake.
So I guess the moral of the story would be to buy an Impala instead of a Malibu....(if you even want to buy GM in the first place)
Ian