Scaling is basically telling the ecu an accurate flow capability of your injectors. The only way to know the correct info is to have the injectors flow tested. Some aftermarket injectors come with test data, good ones at least do. In megasquirt it’s done with “req fuel” and “dead time”. Those parameters along with entering the correct size (ie 1000cc or 750cc or whatever yours are) must be stupid accurate. If you have 1000cc injectors and they flow 993cc at your fuel pressure and your ecu thinks they flow 1000 then all the calcs will be off.