Heinz, that is very interesting.
I think most people think of the ECU controlling the throttle, fueling etc.
But on a cable operated throttle body the Idle Air Valve does indeed act like a miniature drive by wire throttle body so rev hang could occur by the programming of the table in the ECU that controls the IAV.
When I think back to my early experience with my old Zetec, I had forgotten that I used to feel that the gearshifts were slow because it took too much time for the engine to slow down on upshifts.
When I changed the ECU to Omex and was able to programme the IAV to my requirements, the gear change was much slicker because the IAV remained closed under those circumstances. In effect, slight but noticeable rev hang.
BTW it was the same flywheel so that did not affect the inertia of the engine.
Fascinating subject.
