Spec II is a mod which expands upon the core Gran Turismo 4 experience, bringing a variety of fixes and improvements to the game. As the name may suggest, Spec II primarily aims to improve on the game in ways that feel Polyphony Digital themselves would, while also adding a few modernised features and challenge run-friendly options. Spec II is based on the NTSC version of Gran Turismo 4 Online Public Beta and is distributed as an xDelta patch requiring this version.