I have a pressure washer that is 3gpm 3200 PSI I want a downstream injector but realized there are different sizes and I can’t find a straight answer on which one I need. Do I match the 3gpm provided by my pressure washer? Additionally, each injector size means a different chemical dilution ratio based on GPM from washer.. I think. So if you have the approximate chemical to water ratio I will be getting with an appropriate sized downstream injector then I would really appreciate it. Thanks.