[P.J.]

Phosphoric acid and Nitric acid dip is the best nothing cleans aluminum better. I used it in the manufactoring of aircraft tooling for years. You can find a local aluminum
treatment company and ask if they will dip it for you.Those chemicals
are to be handled by pros and with the right equipment. Sand blasting your intake is not recomended as it is like adding sand in your gas tank use glass.
Peter