Fuel additives including Redex don’t really* get anywhere near the inlet ports of a diesel and so do nothing to help minimise or remove diesel inlet port deposits. The main area of interest is injector nozzle cleanliness.All it takes is a couple of videos showing the inlet ports on an older diesel and it's enough to terrify me into using V-power diesel... AND throwing in some REDEX every now and again for good measure...
*Some fuel inevitably makes its way into the sump. So in the limit, a very small amount of fuel additive chemistry ends up being carried into the intake system via the blow by gases, but these will have very little impact on deposits.