We specialize in turbo applications and have extensive experience on BMW, Audi and Mercedes modern gasoline direct injected engines. There are numerous reasons for manufacturers moving to direct injection vs traditional methods; precise fuel control.  One of the disadvantages is the creation of carbon deposits due to internal engine tolerances/leaks... 

Walnut blasting is recommended by these same manufacturers as the method to safely and effectively remove these Carbon deposits.  The difference is felt immediately; and often quite a significant difference in several areas; performance is the main one for most folks.  a typical BMW n54 with 150k km can gain significant HP improvement. A gain of 37Whp was measured on one clients car after a walnut blast.  on a 306hp engine; that is significant.. Results vary, but, almost everyone notes the improved performance and better fuel economy.

There are countless benefits that come from performing intake valve and chamber cleaning which include: