Additives are okay for preventitive maintenance, but your fuel injectors have small filter baskets in them that an additive can not clean. The best thing to do is pull your fuel injectors, and send them to be flow tested and utrasonically cleaned. We charge $17.00/injector for automotive top feed injectors. This includes before and after test data, cleaning, replacing the filter baskets, and replacing the o-rings and pintle caps if needed. Let me know if I can help you.