Diverter/Deceleration Valve
The diverter valve is used to prevent backfiring in exhaust system during sudden deceleration. The valve senses sudden increases in intake manifold vacuum, causing valve to open and divert air away from exhaust system. This allows air from the air pump to pass through valve and silencer, out to atmosphere.
A pressure relief valve controls system pressure by diverting excess pump outlet air (developed at higher engine speeds) to atmosphere through the silencer.