If you look at a egr valve that's been taken out you will see that no amount of additives or sprays are ever going to clean it. I used oven cleaner on my one and it cleaned it up nicely. Bit like having gloss paint on your hands and trying to wash it off with water.
best thing for a turbo is more than regular oil changes good for the engine as well best thing for an egr valve is not to have one or blank it off anyway :d
for injector cleaner try a motor factors they sell a cleaner that is much better that the normal garage additive
Ive allways been a little wary of additives and injector cleaners, the feeling that theyve got to be "thinning" the mix to dissolve stuff.and since the hp pump relies on the "thickness" of the diesel for proper lubrication.
Some further reading on google warns of additives causing water droplets to get thinner than 2 microns or some such,get past the fuel filter and..not good for your pump either..
Having said that ..since my fuel system is delphi and delphi extoll the virtues of their own diesel additive on their site(well they would wouldnt they). Id use that if I was going to use anything.