After a humbling bankruptcy and $50-billion government bailout in 2009, GM has rebounded with steady profits and a fresh lineup of competitive vehicles. But the next stage of the comeback poses new challenges for GM as it tries to make up for lost time when it suspended many of its product programmes. Now GM is focusing on beefing up its roster of higher-profit, luxury models for its Buick and Cadillac divisions. On Tuesday, GM presented a new small Buick SUV called the Encore. While GM?s sales in the US increased 13% last year, executives acknowledge that more growth was needed to improve profits in 2012.