Yes there is 2nd spec in the ECU pinout.
For stock S13 it's 1.6V idling and 2.2V at 2,500 rpm no load.
While bench test is
Approx 1V static and approx 2v blowing.
Trouble is any Z manual will have idle and high idle voltage for a 3L engine sucking on it, so you need to find the bench test.