Another angle: "2 mpg top" might be "2MPG Top" in a branding context. Maybe it's a product or a specific track. The "2" could indicate a version number or a sequel. "MPG" could stand for something like "Maximum Power Generation" in a creative context, though that's speculative. Alternatively, in music production, mpg isn't a standard term. Maybe it's a mix of "MP" (maybe Mastering Production) and "G" (Generation?), but that's a stretch.