Reuters: Sirius XM Holdings raised its full-year forecast for revenue and subscriber additions for the second time in a row, citing strong U.S. auto sales. Sirius XM said it now expects to add 1.8 million net new subscribers this year, up from its prior forecast of 1.4 million. The company had first forecast addition of 1.2 million subscribers in January. People who buy new cars fitted with Sirius receivers usually get free access for a few months, but must pay a fee to continue the service.