For decades, Pontiac seemed to do no wrong. The brand built honest, fast, and affordable muscle cars, from the golden-era GTO to the Trans Am made famous by Bo "Bandit" Darville and KITT in Knight Rider. By the late 2000s, though, Pontiac was fighting for relevance. Then came a car that should have changed everything: the 2008–2009 Pontiac G8 GXP. It was effectively a four-door Corvette,...