i dont think i spelled it right, but whats the difference between high and low inpedance injectors?

The primary advantage of low impedance injectors is a shorter triggering time. When large injectors are fitted to high output engines, low impedance injectors will often give a better idle quality because of this fact. The primary advantage of high impedance injectors is the fact that less heat is generated in the drive circuit and often no external resistors are used.

so if i buy 550cc injectors, and they are low impedance, i need an external resistor pack?

Just use high impedence injectors.

But yes, if you use low impedence, you will need some kind of resistor.

Are you gonna use the stock fuel rail or switch to top feed?

im hopeing to use the stock fuel rail.

Then just do nismos or something. Drop in replacements. Anything that fits the SR rail fits the KA.