i'm pretty sure this is answered somewhere else on the site, but its shitting me seeing this unanswered thread.

they are side feed, high impedance. and yes, you do need to know the impedance. sr20's being what they are though, you should be able to pick up aftermarket units anywhere so you shouldn't even have to think about this, you should just tick the box that says 'sr20det' when you're ordering. don't fuck around with 2nd hand injectors from some other car with different plugs and what not if you can get direct fit aftermarket units. one thing i love about not owning a u12 anymore is that for a small price premium, i can buy stuff that just bolts right in.

a very basic rule of thumb for inejctor sizing is

flow in cc / 5 = hp per injector (at the crank)

so if you wanted to start with the power of your car, assuming your 200kw is at the wheels, we'll allow for 30kw in drivetrain losses and go from there, multiplying by 1.34 to get hp

((power at crank in kw * 1.34) / 4) * 5

((230 * 1.34) / 4) * 5 = 385cc injectors

that would be at 100% duty cycle however, so you want to add a bit of meat. a maximum of 80% duty is generally pretty good. so you'd want to multiply the figure by the inverse of 80% - the inverse of 0.8 is 1.25

therefore 385 * 1.25 = 481.25cc injector size @ 80% duty cycle

easiest to grab around that size is 500cc