[ProwlerGT]

Couple of maybe new ideas, but first..... where is your mods list? Can you add that to your sig? I think that would help others help you.

1. Since the problem seems to change RPMs (raises) due to colder air then how about we focus on the following: BAROMETRIC PRESSURE SENSOR, Engine coolant temperature sensor, and intake air temperature sensor - You need a test harness at the ECU connection point. See about obtaining a broken ECU and harness with at least 1-2 feet of wire on it from a junked 3000. I've never done this, but this is how I would. Remove the connector from the broken ECU and attach it to the test harness with the wiring (take your time and make it a good setup). Find the pins/wires that are responsible for the aforementioned sensors and remove the sheath on the wiring just enough to clamp some alligator clamp jumper wires on - hook that to a multimeter. Once done plug it to your car's harness and ECU connection point and observe the voltage during the trouble RPM range for each sensor 1 at a time.. not all at once (1 at a time to reduce risk of arcing during testing; electrical tape over the spliced wire areas when not in use on the test harness). Know ahead of time what voltages stand for what temperature or pressure and jot down what you see. If the voltages are ACCURATE then this leads me back to the ECU for electrical.
Do you have any ground wiring issues? Can you test your ground and see if its good? Did you ever get the chance to swap ECU into your friends car?

2. Is there a way to trick your ECU into thinking its running at 200 F when its cold? Curious to see what the ECU would do if it already thought it was warmed up. Maybe this isn't a safe test for the engine though. Thoughts?

3. Variable Induction Control Motor and Induction Control Valve Position Sensor - Have you tested these? Very dirty valves??????

4. Turbos - I don't know if you've upgraded beyond stock Turbos or not, but perhaps it happens on some people's cars (mind you I still think its the ECU) and not others cause its a physical/mechanical wear issue. Is it possible to run the engine without Turbos connected or would that not work at all? Maybe 1 or both turbos have seen their life.

5. Remove your exhaust - all resonators, cats, precats, or mufflers - See if you still have the problem. This is just a WILD shot in the dark.

6. What is your alternator voltage during the misfire?