Lawmakers on the Republican side of the aisle have given Apple a stern warning. They told the company that if it starts sourcing Nand flash memory chips that store data for the iPhone from China's Yangtze Memory Technologies Co. (YMTC), Apple will have to deal with increased scrutiny from Congress. Apple has told the Financial Times that it has not used chips from YMTC in any product but it was "evaluating sourcing from YMTC for Nand flash memory chips to be used in some iPhones sold in China."U.S. lawmakers are upset that Apple is considering using chips from a Chinese…