Of all the concept vehicles coming to the Detroit auto show this year, the two youth-oriented concepts from Chevrolet will be the most divisive. They're either a savvy marketing move or a return to the worst bad habits of old General Motors. Chevy says the pair of compact hatchback coupes — dubbed Code 130R and Tru 140S — are marketing studies that GM will research with young buyers. Both are powered by a 150-hp turbo 1.4-liter engine that could reach close to 40 mpg. The Tru 140S draws from the Cruze parts bin and drives its front wheels; the Code 130R is rear-wheel-drive.