The walnut blasting kit I used: https://amzn.to/3yVUgMU
There’s one major design flaw that affects direct injection engines, and that’s the reality that the intake valves will end up getting a bunch of gunk and carbon deposits built up after some time. Normally on port injection, fuel is sprayed on the backs of the valves so they tend to stay cleaner. Because the fuel is injected directly into the cylinder, this is not possible and the valves will accumulate gunk.
One way to clean up the intake valves is to use crushed walnut blasting. It’s just like sand blasting but instead of using sand as the blasting media, you use crushed walnut particles. They are soft enough to not damage the valves or your heads, but hard enough to remove the carbon deposits and clean up the valves nicely.
In this video we use crushed walnut blasting to clean the intake valves on my Ferrari 458. The process was fairly simple and the results are very impressive. I also felt very comfortable about the low risk of error.