SILZKBR8D8S,97506,NGK 97506 SILZKBR8D8S. SILZKBR8D8S,97506. Spark Plug. Material Iridium. Electrode Material: Iridium. Material: Iridium. Spark Plug Reach: 26.5 mm. Your kindly understanding and great patience would be highly appreciated!
These plugs are perfect for the N54 with any upgraded tuning. 1 step colder plugs work very well on my stage 3 turbos with .02 gap and 485hp. the plug replaces the discontinued 5992 plug.
Absolute best spark plugs for a modded German vehicle- especially Bmw S-63 / N-55/ N-54 - Non Stock colder plug . 
Best spark plugs for a 2007- N54- N55 - S-63 (tu) - or non - if you have your car modded - if not still amazing/ colder then stock so once you have a non stock car Tuned w/boltons - or whatever this is the best plug you can get for a turbo or TwinTurbo vehicle! Period (if you have worked onto the vehicle they should be gapped at. 22–. 24 The stock gap of the plug is .16 - just fyi 
These plugs are great and the only ones that I use in my BMW 750. They fire smoothly and allow the engine to be smooth running. The price is fair and they run great.