I used a wire wheel. Worked great. I also painted though. You planning on painting it? You can find paint thats pretty close to the natural look if thats how you want to keep it.
My intake looked somewhat similar to that... started turning almost a green color.
I basically just scuffed it up with whatever scotch brite pad i had (maroon?), cleaned it, and sprayed it with like high temp silver brake caliper paint. Turned out great and looks like a 'refreshed' stock intake.