On 2009 X5 4.8 had the injectors deep cleaned. The result is amazing, the car is pulling much better. Feels like extra 20-30 hp. The procedure involved removing micro filters (they were so dirty and brittle at 89k), cleaning (using a gizmo from eBay and 9v battery) with brake fluid, then with seafoam, and finally with carb cleaner; installed new micro filters, new o-rings. Put everything back with a little bit of dielectric grease.