There is a geezer near me fitting hydrogen cells, apparently they work better on diesels. They reduce you emissions so much so you can re apply for you cars emission grading and this will affect your road tax and things like ULEZ etc.
Do you know if this is true? I have yet to phone the bloke.
About 10+ years ago, I had a mad Yank from deep south arrived as a customer, you could tell he was mad by the patchy shaving he had done, you know the type. He had made a hydrogen cell and was offering to fit it on my Misses Passat. I understood the method/science behind it, but was reluctant