Siemens injectors are defo very good...but I assume you have the means to adjust fuelling and control any new injector ?

I was using some Siemens 660cc in my car for a while ( non cossie ), at 4.5 bar base pressure, with up to 1.3 bar on top of that.
They worked perfectly for me....

Almost regretting changing them to larger 750cc RC Engineering injectors, but the others were too small.