i made 353 rwhp with my stock 444cc injectors at stock booste using sds and the injectors were maxed. i upgraded to 680cc injectors and got 392rwhp at 15 PSI booste and the injectors were right at 85% duty cycle.
Depends on what year rx7 you get the injectors from. the fc modle all had 550 injectors and i do believe they were low impedence. you can find them pretty cheap on ebay i would have them cleaned and flow checked at RC eng to ensure you are getting 6 injectors that flow about the same.