How can you tell if your turbo not working?

You can tell if your turbo isn't working by noticing a significant drop in engine power and acceleration, especially at higher RPMs. Additionally, you might hear unusual noises like whistling or grinding from the engine bay, and you may see a decrease in fuel efficiency. Check for warning lights on the dashboard, as well as any visible signs of oil leaks or damage around the turbocharger. Finally, perform a boost pressure test to confirm if the turbo is generating the expected boost levels.