Well, the Injector impedance is the ONLY thing you need to check, as some ECM does not have inbuilt drivers to run low impedance injectors.
You can check the impedance easy with a multimeter, just check the injector resistance in OHM and it will be anywhere between 0.5 to around 4.5 for low impedance injectors and 10 OHM+ for high impedance.
The size doesn't matter at all, you can change youre injector scaling in the software. As you as you start the car, its pretty easy for the tuner to make it idle and the injector scaling will only affect youre number size in the VE table (MS and most other commercial ECMs dont have a true VE table, just random numeric table).
regards
/DJURET med Evon