Here's some pics of the intake wheels after polishing in a tumbler for 35 or so hours. You can see a BIG difference in size. If you decide to do this yourself be careful. The vains are delicate and I was using corn stalk with Flitz polish additive. Works great but the corn stalk is shot now and I have to buy more Flitz for my case polishing. Some of the carbon build up will have to be carefully scraped off. Some of it is really hard and doesn't come off easily. Use a very sharp knife of razor and scrape carefully.