Bosch AMM (MAF) adjustment screw

[bjanesi at juno.com]

I am investigating the replacment of my stock VAF meter (Merkur XR4Ti)
with a Bosch AMM, as used in many (Saab, Volvo, MB) LH-Jetronic equipped
cars.  And yes, I do know about the Pro-M MAF replacement (that would be
too easy).  As you may know, there is an adjustment screw on the Air Mass
Meter, used for fine tuning of the idle mixture.  My question... What
specifically is being adjusted here?  I always assumed it was the base
voltage output from the hot-wire.  However, I've recently been told (by
someone who seemed to know what they were talking about), that this is an
entirely separate circuit which adjusts the injector pulse width at idle
(only).  Anyone have some definitive data on this?  If it is a separate
circuit, that makes this a more challenging project since this function
would not be supported in the Ford EEC-IV found in the Merkur.

Specifically, I have an AMM from a Volvo 230FT motor (2.3L Turbo); Bosch
p/n 0 280 212 007.  If anyone happens to have the schematic for this,
that would be real helpful.

Thanks,

Brad Anesi
'88 Merkur XR4Ti 5-speed
'91 Alfa Project 164Q 5-speed

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