The invention provides a manifold block (140) for improving the efficiency of an internal combustion engine. The manifold block is arranged to be located between an inlet manifold and a cylinder head of the engine (130), and comprises a block of material having at least one manifold channel (110) there through. The manifold channel has an input end and an output end, wherein the input end is connected to the inlet manifold (102), and the output end is connected to the cylinder. The manifold channel includes at least one injector head channel (132) located towards its input end and adapted to receive a fuel injector. The manifold block may also incorporate one or more induction regulators for improving the efficiency of fuel/air mixing in the manifold channels (104, 106, 108, 110).