Take a look at my first post in http://www.cruzetalk.com/forum/34-1-4l-turbo/46833-new-copper-spark-plugs.html. I did some computations on my OEM plugs when I pulled them and figured out why GM came back with 0.025-0.028" for the plug gap when installing them.I checked my gap on my 2013 Cruze LTZ, 1.4L Turbo. 3 our of 4 plugs were just under .025", one was just over .025". I re-gaped them all to .036.
I can't say as I see any huge differences in the way the car runs. It might possibly have a little less lag from a dead stop, and maybe gets slightly better gas millage ( certainly not any worse ). If I am seeing any real difference in MPG, it's probably 2% or so. ( went from 35.4 to 36.1 MPG in my daily driving, which is about 70% high way (70MPH ) , 25% two lane blacktop rural hwy (45 to 55 MPH), 5% small city driving (very few jack rabbit starts or stops) ).
For GM to 'fix' the problem of the GAP not being right, I suspect they'd have to get the spark plug maker to 'fix' the problem. I highly doubt that anyone at GM is going to be re-gaping mass quantities of plugs. Also, the 2013 Cruze owners manual still lists .028" gap for all engines. Meanwhile the average person owning a cruze would likely never notice a difference between having their plugs at .025" vs .035".