By Giulio Piovaccari and Nick Carey MARANELLO, Italy (Reuters) – Ferrari makes some of the fastest cars on the road, but the luxury Italian automaker is taking the slow lane to an electric future as it tries to overcome the technology’s disadvantages against today’s powerful fossil fuel engines. At an investor day this month, executives promised a new era, with the first fully electric Ferrari in 2025. But for now, combustion engines remain the noisy heart of what it does. Unlike some rivals, Ferrari has not provided a roadmap for going all electric. Volkswagen’s Bentley brand and Volvo are bo…