SULEV is an acronym for Super Ultra Low Emissions Vehicle. SULEVs are 90 percent cleaner than the current average year's models. SULEVs emit substantially lower levels of hydrocarbons, carbon monoxide, nitrous oxides and particulate matter than conventional vehicles. The SULEV standard steps up the ULEV, Ultra Low Emission Vehicle standard.
Some PZEVs fall into this category by default--buy a Toyota Prius in CA and fuel it up, it's a PZEV. Drive east and fuel it up over the next 2,500 miles and it's an SULEV, since CA's low sulfur gas formulations are not available everywhere.