Some cars can be reflashed, for example my Mini Cooper S was reflashed when I increased the boost, but this car was boosted to start with. I am not an expert but I think some stock ECU run into problems dealing with boost when they are only programmed only to see vacuum. I know that people who add turbo's to non turbo'd cars usually add a piggy back system that works with the stock ECU to adjust A/F under boost conditions.