I got radiator water on my manifold and it left a brown/gray stain that won't come off. I've tried windex with a tooth brush and brake cleaner with a rag--no luck. Is there a way to get rid of it? My manifold is that rough blasted steel texture. Tyler

Here's a pic

 

I bought some cleaner called 'Purple Power' that I found at an O'Reilly's auto parts that cleans and degreases real well. Try a small section first, I did notice when I cleaned my anodized air cover it left a tainted spot on it when I left it too long but I don't think you'll have any problem on the aluminum intake.

 

try using carburetor cleaner on a cold intake manifold.

 

Get a product called Wheel Brite I think it is at Napa. It is used to spray
on and hose off aluminum wheels. It will clean any aluminum anything.