Hey...I found a trick that I'd share with you guys!
I just did this last week, and my engine is *still* in perfect shape!
Tire Wet N Black - normally used as a tire dressing that really looks wet...well, n black

I sprayed it over *everything* in the engine bay - from angles to head-on - so far it repels dust and water and my engine bay looks just like I did it a week ago, even after washing the outside of my truck 2 times since then. I 4X alot, and I would have thought that stuff would collect the dust, but I also knew it's not hard to get off...well, it appears that it's REPELLING the dust! Give it a try - I'm not disappointed!
Psychlone