If it is bad that the injectors area 15-20 year old design that must mean the cossie engine is also crap!!
The injectors are MUCH older than that, but still do the job perfectly.
My car on greens goes all the way to 7300rpm in each gear too , does 34mpg sitting on motorway, around 28 little runs.
As for pushing the limits of the injectors, you just go up a size.
I only have at the moment 330bhp, (330lbft,from2200rpm all the way to 6500rpm) but at 1.4 BAR.
As the siemens seem a newer design they should be better, oh I DON'T have closed loop on mine.
tabetha