What's the target temperature of the airbox thermostat system?
My car is an LH2.4

AND - what air temperatures will kill the AMM? I think it's safe to say that 100 or 105 deg. F should be safe, as such temperatures do occur naturally in the hottest summer weather in some parts of the world. But how hot is too hot?

From reading Bentley's and examining the airbox it looks like it's set up to warm the intake air if the ambient air is below 60 deg. F.

Bentley's says the flapper is designed to select only cold (front source) air above 59 deg. F and only preheated below 41 deg. F. From examining the mechanism it looks like it's measuring the incoming front-source air only (not mixed air) via the small air funnel from front of airbox aimed at the temp sensor inside.

I want to reinstate my formerly disabled airbox thermostat for fuel economy reasons. To protect the AMM I've purchased a digital thermometer which will let me read the airbox temperature so I'll be aware if that thermostat fails. ($10 at Autozone, also similar available at JC Whitnmey)

I also have the option of rigging up an alternate source of warmed air, such as using a mix of post-radiator heated air (my e-fan conversion leaves open space between rad fan and timing cover area).

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Sven: '89 245 NA, 951 ECU, expanded air dam, forward belly pan reaches oem belly pan, open-front airbox, E-fan, 205/65-15 at 50 psi, IPD sways, no a/c-p/s belt, E-Codes, amber front corner reflectors, quad horns, tach, small clock. Wifemobile '89 245