Oh, and it idles fine at first crank when cold because cold-start enrichment is active plus high idle. It's when you warm up enough for those routines to shut down and the ECU wants the engine to idle at stoich that you notice the fuel trims aren't right for the current combination of ambient temperature and pressure.
You also lose the zero point on the electronic throttle body which isn't so obvious when throttle angle is held high for high idle. It takes a few ignition on-off cycles for that to re-calibrate itself. You can help it out by allowing the gauges to do their full sweep cycle between turning the ignition on and cranking the engine.
Terrible things like this don't happen where I come from. Other terrible things happen instead.
Obligatory 'build thread