Good question. I have two Cruzes with the LUW, and I've wondered about this myself. Hopefully, someone who knows definitively can reply.I have a 2011 Cruze 1.8L VIN H, LUW. I found a 2013 with a 1.8L VIN G, LWE. What is the difference between these engines. Why do interchange programs say they don’t fit? How can I make this engine work in my 2011?
In the mean time, here's what I've learned thus far. GM Authority says they are identical.
Wikipedia states that the LWE adds secondary air injection.
Lots of on-line parts vending websites ask if my LS is flex fuel or gas-only, as if to imply that may be the difference between LUW and LWE.
And perhaps air injection goes with flex fuel.
All that said, my take is that the engines are nearly identical. <speculation> You could probably use most of the new one in place of the old, keeping the old intake and sensors as well as the old computer and fuel system, thus avoiding the need to re-program or re-plumb anything.
If there is indeed an air pump on the new one, I would expect it to get left out with the intake swap.
Ideally, someone who has done this will chime in. For now, hopefully you know a little bit more about it.