Air. Every car wash I just go over the engine bay with a compressor air gun and a soft bristled brush to get the dirt loose. To make the plastics pretty, I've used VRT or Adam's In & Out Spray. Armor All gets really greasy and will attract dirt to the surface you put it on. After a few hundred miles, you'll see the dirt start to cake on some surfaces.
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[09][MB][6-Spd MT][Touring][Stillen Gen III][K&N][Borla CBE][Evo-R]
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