SRS EXHAUST SYSTEMS 4-1 HEADER 2.5" STAINLESS STEEL (HONDA B-ENGINES)More power from your B series engine with SRS manifold 4 1 2. 5 inch stainless steel Do you really want to get the most out of your B series engine? Then choose the SRS manifold 4 1 2. 5 inch stainless steel. A 4 1 manifold delivers maximum power gain at high rpm, and certainly in combination with the 2. 5 inch connection. 4 1 = Maximum power gain at high rpm Including connection 2 lambda sensors 2. 5" cat replacement test pipe needed for assembly The