I do hope that's not the idle CO ?, if so it's a piss take imo.
I was on greys T34.48, with a 200,000 miles engine(head was done, but original bores,piston, rings), so worn that it nearly was too worn to get a clean bore with 1st oversize and nearl skipped that to 2nd size!!
This was putting out 0.97% CO, 137 PPM on greys, unadjusted for mot, pisses through the mot, I could adjust it on the lappy if needed, but not needed.
THIS IS NOT ON CLOSED LOOP, although that is a feature that I have on ecu it is not enabled.
Did I forget to mention that I was on a different ecu ?
My car ran 100% perfect, would return 40+ mpg on a run, and didn't have a single hiccup anytime anywhere, would pull 100% cleanly from 900 rpm top gear hot or cold
I would say the greys are perfectly able to do the job perfectly, so if you have them I wouldn't swap, IF mapped correctly you can get good results on a good ecu with greys, if buying from scratch I would get siemens only as they are still made whereas the greys are not.
tabetha