The air has to come through the AFM. If you run a filtered external source you'll run way lean when the valve is open. The valve should be placed where the AAR was.

You could probably plumb in a later model AAR that might have a little more engineering in to it to make it more robust. But the basic design has lasted many years.

Those later ones are really big, which is fine for an ordinary passenger car. On a sporty car, I like to minimize stuff

The air has to come through the AFM. If you run a filtered external source you'll run way lean when the valve is open.

True that. I agree and wouldn't recommend an underhood filtered source.

Not to say that you couldn't find a more unobtrusive location for a small solenoid valve and it's associated tubing and wiring, but wherever you pick the air source from, it's molecules should be included in the AFM flow.

It looks like the newer engines have the IAC controller on the intake manifold, and the ECU must be compensating for the extra air.

So right now, now matter what kind of valve system you use, it looks like you can't get away from the same kind of idle air arrangement, meaning you need to gt it from the same point on the intake tube, which is something that gets dried out over time and cracks from the vibrations.

Capt.- Probably just as chilly down here (Norfolk) as Philly. Starts fine, well, a little lumpy, but no stalling or pressure on the pedal to stay running

WILBY has never had an AAR since I've had her, there's a block-off plate installed by a PO.