i asked same ? while back, no one answered. so i went out to find my own, and found that stock ecu can only handle up to 310cc injectors. with 450cc injectors/stock ecu, car will not hold an idle, it will stall. but if you are not in that situation (hondata or something like that), the injecters will have a very tight fit using stock injector seals but they will fit. some company, i don't remember which makes seal that have a larger I.D. than stock that will work well with the larger mitsu injectors. hope that helps and good luck.
the resistor box makes the dsm injectors have the proper impedance so the ecu doesnt burn out- and the ecu will idle the injectors...all you need is a device called a smc. I have never used it, but ive heard a lot of good things about. I think it would be good for someone that doesnt have the money for a hondata.