Hi,
Don't know if this is any help. I have been using Redex for years every time I fill up with diesel. half a bottle to usually 3/4 tank of diesel in my old 2.0 Passat. I had never any issues with injectors and done over 280,000 miles on it. I had to take the engine out (200,000 miles) and in the process had to remove the ERG. It was completely carbon free. I saw my mates ERG which he had to get cleaned and it was bunged up after 100.000 miles. Was it the Redex? I wait till Tesco's do it for half price and buy a pack of it £2 a bottle. They also co DPF cleaner for £4 (half price) and I dump it in now again.