taurus code p1131

While idling at stop lights my rpm will dip from normal range 750ish down to
450ish and then spring over 1000 then settling back down to normal. I can
feel an obvious sluggish shake to the engine when it does. however this is
not every day and/or every time its a little intermittent.
Error code I was told is P1131

I just want to confirm air control is 100% cause and that changing is worth
what its going cost me to have it done.