Since there are 16 BLM cells, and they're there account for changes in operating conditions, weather, etc. It would be unrealistic to spin your wheels trying to get them all at 128 (can't be done). If your idle cell(s) are somewhere between 118-138 then you might try tweaking fuel pressure if you're bent on getting them perfect (but they won't stay right there all the time).
Those cells are there for a reason, as long as none of them are run up against their stops at the top or bottom end, leave them alone, and let them do their job.
