The effect these acids have on austenitic stainless steels like 304 and 316 depend on many factors including the concentration, the temperature, the impurities that are present, velocity, and even whether they are mixed together in some combination or not. Worse, the corrosion rate can change in unexpected ways. For example, intermediate concentrations of sulfuric acid are more corrosive to these stainless steels than very dilute or very concentrated solutions. One thing that can be said is that 304 and 316 stainless steels are not recommended for hydrochloric acid of any concentration. There is much information in the literature about the corrosivity of acids toward austenitic stainless steels. I suggest you consult one or more of these references after you have gathered the details around your specific situation.