Laugh all you want, GM’s 2-Mode hybrid system is pretty impressive. When equipped with an electric motor and batteries, the Chevrolet Tahoe 2wd jumps from a mere 12/17 mpg (city/highway) to a more tolerable 21/22 mpg (city/highway). Not too shabby for an eight-passenger leviathan. Now it looks like The General is investing plenty of time and money into slimming the...