Generally speaking, a Mini Cooper with a 1.5-liter turbocharged engine and a 6-speed manual transmission will have an RPM of around 3000-3500 when cruising at 70 MPH in fifth gear. This RPM range is considered normal for this specific vehicle and engine configuration.
However, it's important to note that different Mini Cooper models and engine variants may have slightly different RPM ranges at specific speeds due to variations in gear ratios and final drive ratios.
If you are concerned about the RPM of your Mini Cooper, you can refer to your vehicle's owner's manual for the recommended RPM range for different gears and speeds. You can also consult with an experienced mechanic or automotive technician for a more accurate assessment.