@dc42 Thanks for confirming that using a spare heater port is a better option for an air pump.
Yes, I will be installing a flyback diode.
However, would it be beneficial if I use two? One screwed in at the heater port terminals to be closer to the mosfet, and another at the motor to reduce any interference created by the PWM?
Also, will the heater port pwm up to 25khz, as recommended in other threads?