Former CEO of Citigroup Vikram Pandit is collaborating with Steven Levitt, co-author of the popular “Freakonomics” book series to launch a new consulting business aimed at helping companies improve their cultures and use of technology. The firm, called TGG, is promoting a novel approach to address the challenges that large complex organizations face in compliance, fraud, corruption, and culture and reputation, according to Hamid Biglari, one of Pandit’s former Citigroup colleagues and a managing partner of the new venture. The venture is based in Midtown Manhattan. According to Biglari TGG’s partners include besides Levitt, Daniel Kahneman, a winner of the Nobel Prize in economics.The duo has already helped create a Chicago-based consulting firm called The Greatest Good. A planned partnership between TGG and The Greatest Good is not yet completed, according to sources. The venture is the latest effort by the 57-year-old Pandit to bounce back after leaving Citigroup.