Mine runs greys, idle is 100% perfect as is whole running, can do 40mpg, mot pass was easy at 0.97% CO 137ppm, with 200K miles on the engine, T34, modded head etc, NO CLOSED LOOP gimmick in sight, even though my ecu does it, as well as adaptive, I run purely mapped.
Cold idle is perfect, even though my ISCV does not work at all.
There's nothing wrong with siemens , but if the greys flow enough for what you want, why spend money on different injectors, buy other bits instead.
tabetha