What happens if none of them flow match?
Flow match means that all the injectors you have flow within a small percent of each other. Further off each injector is more lean or rich that one cylinder will be compared to the others. If they are too far off then yes you can have horrible issues. You can also get them flow tested for $6-$8 an injector which you should do no matter where you get them from. Most of these injector companies are flow matching the injectors, putting their stickers or cases on the injector and up-charging you $1K-$1500.