I don't like the idea of steam as its basically particles of water so more likely to get in places like electrical/engine components.
Low pressure setting on the jet wash. Spray with a decent APC or degreaser like Megs or AG. Brushes, cloths, anything that will get into the nooks and crannies. Then low pressure jet wash down.
Simple point - don't be stupid. Don't aim the pressure washer at the TB or leccys and you'll be fine.
Dress the plastics with 303 aerospace or AN Other trim dressing, metals polished, paintowork polished and high temp waxed etc.
My old clio;