Cylinder heads on T-Series long block engines are 1999-’05 style. Owners of 2006 models will need to purchase a set of 1999-’05 style, offset intake flanges such as S&S #106-3516. Cylinder heads on these engines are specially machined to compensate for the non-stock cylinder length. As a result, they are compatible with manifolds and throttle bodies with stock length intake runners. In addition, the breather vent bolt locations have been adjusted so they are in the stock location, so stock style air cleaner back plates will bolt up to these engines. 1999-’01 EFI engines equipped with Magneti Marelli® fuel injection will require a performance tuning module such as the DynoJet® Power Commander® 3 or S&S VFI module. The stock dual-bore EFI throttle body is not adequate for T111 or T124 engines. The S&S 58mm EFI single bore throttle body is highly recommended to achieve maximum performance. 2002-’06 EFI engines equipped with Delphi® fuel injection will require a performance tuner such as the DynoJet Power Vision® tuner, Harley-Davidson® Race Tuner, or S&S VFI module. The stock single bore throttle body can not supply adequate air for these large displacement engines. An S&S 58mm throttle body is highly recommended for maximum performance. Carbureted engines will require a performance ignition module that allows adjustments to the advance curves. The stock ignition module is not adjustable, and use of the stock module will likely result in engine damage due to knock from incorrect ignition timing. Performance carburetors are recommended to achieve maximum performance. S&S Super E carbs are ideal for T111 engines in touring applications, but a Super G will produce more top end horsepower. S&S Super G carbs are recommended for T111 engines in performance applications, and for T124 engines in all applications. Not legal for sale or use on CA or EPA pollution controlled motorcycles.