I grabbed a image:
a second image
The big offenders are all the leading edges of the motorhome.
*The nose above the cab should be more like an AIRSTREAM trailer or motorhome.Very bulbous,which really helps in crosswinds and guarantees full flow attachment onto bottom,sides and top.Consider having an awning company construct a rolled aluminum superstructure and fabric cover which would mimic (without compound curves) what AIRSTREAM does.
*You would need full-height,12-inch radius fairings attached to the doors themselves which,when closed, smoothed the airflow onto the sides,killing the separation which is there right now.
*Everything on the roof should be streamlined as Orbywan has done with his Ford-based motorhome.
*I streamlined the front of my next door neighbor's Toyota,just like yours,with sheet aluminum grille-block,airdam,with rolled-radiused outers.Since you will at times need all of your radiator,consider blocking only the grille opening which is not directly ahead of the radiators tube and fins.Extend the dam down even with the lowest suspension members.
*Run your side skirts at the same elevation as the bottom of the new airdam.
*The rear wheels could also be enclosed within skirts.
*Consider some length of boat tail after the front is cleaned up,to reduce the enormous turbulent wake which is eating your lunch at the filling station.This wake represents 72% of your aerodynamic drag.