Originally Posted by xr2wishy

they won't aid performance.
basicallythe throttle doesn't snap shut like on a petrol so the turbo still blows through the inlet and pressurises the cylinder. the injectors fire, but metered so that max power isn't achieved and as such drop the power off which then spools down the turbo.
in essence the flow of air from the turbo isn't impeded so doesn't flow back through turbo.