Start
here .
The shield is to prevent excess oil from being sprayed on the underside of the pistons in the deactivated cylinders. The rings would get gummed-up and seize, allowing oil to be burned.
Mostly what I've heard is the problems are way down on '12 and later models. They did get mine fixed, eventually, and it has held for about 60K miles. I'd still be wary, though. I'm not fond of them having to do open heart surgery on my engine 3x in the first 75K miles.
FC
