Which injector do i can use?

You can try nvkush, its reported to work with some 9300/9400 but I didnt get it to work with my 7100.
In general terms you need to be running at least 10.5.6 or latest macbook restore dvd (not sure which one is more recent) as earlier versions are considered to not support onboard gfx at all.

I have tried it with ideneb 1.4. The problem is that the system profiler is showing that i am having 2 gb of ram. But it should be about 1.9 GB (2048 - 128). The other problem is that the system does not boot with nvkush.kext. Is ideneb 1.4 maybe to old?

What problems do you have with your 7100?

I doubt the RAM reported in S.P. matters for anything, I think its just the amount of RAM you have physically installed.
Do you get the amount of RAM allocated for the graphics correctly in the S.P.'s Graphic Section? I dont get any Video RAM reported there for my 7100. For me nvkush never goes into graphical mode, although it finds some card with unknown model.
Like I said, 10.5.6 its considered minimum requirement, Apple didnt have any machines with shared memory nvidias til recently so previous versions nvidia kextx probably know nothing about them.

Did you have entered the device id's into the plist files?

For me the OSX is freezing during boot if i enable the kext. i will try to update the OSX and report what happen then.