Don't. There is no benefit to fitting one whatsoever and due to how the Bosch KE-Jetronic system works it arses up the way the car drives and you will often have stalling and idle problems. Even those who love dump valves will usually admit the RS Turbo drives better without one.

IMHO do not fit one unless you really have to. My Escort doesn't need one and is running 25psi so doesn't have one. My chipped A4 does require a recirc valve due the way in which the fueling setup works, as such it has one.