Depends on turbo, boost and engine management.

RS Turbos do not need them (and never had one from the factory), neither do Cossies. Small turbo Escort Cossie does but not because of turbo damage but beacause of Fords EEC-IV using a MAF that gets very upset by have already metered air passed back again with the closed throttle. Effectively metering the same air twice causing overfueling.