FI is very vacuum sensitive.
Low = intake air sensor
High = Throttle position sensor
So if a low to mid fails, or a mid to high fails, it's something like either or.
Either you have an air leak like look at the intake sensor off the intake manifold and that hose. OR... The intake manifold sensor is the problem.
I'm taking a guess here as to what low would mean in FI speak.
In other words, if the sensor fails, a backup using the penultimate number, calc's the 'best' number as per other parameter inputs.
If there is no intake air sensor like a VOES, then check the throttle position sensor's output as in low signal and if the TPS fails, back to rpm times the penultimate divided by the 'best' the truth table comes up with.
Bottom line, idle is now a closed loop vacuum system. Check every vacuum line off the intake manifold and travel backwards from there.
Said another way, you are one binary short of a happy meal.
