Abstract: Preferred embodiments of an air-fuel module include a manifold and a valve group subassembly. The manifold has a fuel supply passage, at least one air supply passage, and at least one power group subassembly defining a chamber in communication with the fuel supply passage and the at least one air supply passage. The fuel supply passage extends generally along a first axis. The at least one air supply passage extends between a common air inlet and respective air outlets along a second axis A2 generally orthogonal to the first axis. The valve group subassembly extends along a valve axis between a valve inlet and a valve outlet. The valve group subassembly is adapted to be inserted into the chamber through the respective air outlets. In an alternate embodiment, the power group subassembly is formed separately from the manifold so that the power group subassembly can be inserted into a recess formed in the manifold.