Hi all If someone can help, or even point me in the right direction, it would be great. My S4 is running 9° retarded ignition timing. And running rich on both banks. I can't, and nobody else can figure out why. I've changed out plugs, coil packs, fuel filter, fuel pressure regulator, I've pulled and tested injectors. The car runs and feels fine to drive. I only discovered this by chance. I took a test drive in another standard S4 my brother was looking to buy, and I couldn't believe the power difference between both cars. Any and all suggestions will be greatly appreciated guys. Thanks!