Here's my intake manifold cleaning process:
a. 1st blasting is with stainless steel grit for initial cleaning.
b. 2nd blasting is stainless steel round shot, average size .004-.007" diameter, for peening and lustre.
c. Washing with 13 HP pressure washer; 25 degree nozzle pattern, 3500 psi and 4 gallons per minute of water.
All of those steps take a lot of time, and then the finished surface is easily stained once in the engine bay. I decided to powder coat the tunnel wedge intake, and the pair of Blue Thunder competition valve covers. I used a 5% low gloss clear powder coat and the result was excellent. Now all that's necessary to clean off finger prints, drops of sweat, oil mist and dirt is a shot of Formula 409 or something similar and a paper towel.