The RevMeterWidget renders a background image for the rev meter and a dynamic needle on top of it. You can define the positions of the shift light, gear display, boost mapping and RPM value. And you can customize the rev markers.

Don't forget to define input bindings for the engine boost mapping in the input bindings manager here in the editor. You have to define the exact same binding as you did in rFactor to make the boost display respond to dynamic changes of boost mapping during a ride.