P0660 means your ECU doesn't sense the power surge it's supposed to see when turning on the variable induction control solenoid. The system is also called the Mitsubishi Variable Induction Management. It's almost surely either the solenoid itself, or the circuitry & wiring providing power and ground to the solenoid. The solenoid turns a mechanical rod that extends into your intake plenum, and changes the intake airflow at high rpm.
Here's how to check the solenoid. You'll need a multimeter to verify power is getting to the solenoid, and that the solenoid resistance is normal.
And yes, a bad MVIM solenoid can cause a P0300, although there could be something else going on too.