Factory assembly line test procedures shall not apply to light-duty motor vehicles, if (a) the manufacturer thereof advises the state board in writing that the manufacturer does not intend to sell more than 1,000 motor vehicles in California in a given model year, and (b) the manufacturer does not sell more than 1,000 motor vehicles of its make in such a year. Nothing in this section shall be construed to prohibit the state board from requiring testing by the applicable certifying test procedure of up to 2 percent of the motor vehicles of such a manufacturer sold in California. This section shall not apply to 1976 and later model year motor vehicles.