[JohnnyGrey]

The laptop SW set would change the mixture setting to run leaner. We have lots of OEM SW interface tools at work that you can modify settings on different control modules to change settings. Just like someone wanting to run richer, you could use it to run leaner by modifying the flash memory. I just don't think I could get access to a 1996 Ford Aspire setup. What you are changing is the control algorithm rather than the sensor. The settings are not fixed, you just have to be able to change them.

Here's the catch: this only works in open loop mode, which we're not interested in. In closed loop mode, fuel tables are only used for a starting point, and the O2 sensor is god.

The fuel mass is computed from the air mass, of which iat is a correction factor. In closed loop the fuel mass is calculated from the input of various sensors, and is corrected from the output of the ho2s. Ever heard of fuel trim?

ONLY IN OPEN LOOP MODE!!! Seriously guys, I'm getting tired of repeating it by now. Ever heard of long term/short term trim? These are tables that are in the ECU's SRAM that you don't have access to. They're created according to the O2 sensor's output that cancel any wacked out values you put in the fuel trim tables. See that thing on your scangauge that says CLSD LP ? That means your ECU is running off its own tables and ignoring yours.

Where did you get that iat is part of the formula the sg uses to compute fuel usage? I never read that anywhere.

It's true. If you had some real fuel instrumentation that would give you GPH or injector pulse widths, you'd see that tricking the IAT sensor causes only a blip of difference until the O2 corrects it. Then pulse widths go back to the exact same value they were before. The SG on the other hand truly believes that the ECU is injecting less fuel, even though it's not.

And even if you don't touch the ho2s and do the iats resistor mod, you still retain the timing advantage given by the mod.

You might, or you might not. Something tells me that this is one area where the OEM squeezed every bit of economy and performance out of the engine possible on the given fuel. In fact, many engines are eqipped with piezoelectric knock sensors because they constantly flirt with the bleeding edge of detonation. The IAT serves as a starting point and the ECU will see what it can get away with. If you move the starting point well within the knock region, you may cause damage to your engine.