It's not likely to be the TFI. If it were, his car would not run at all. It simply needs the throttle depressed manually, which is an IAC issue or a sensor that's heatsoaked and reading erroneously.
OP, how do you know the IAC is 'good to go?' Was it tested with a scope? Sometimes cleaning them will finish them off.
With a hot engine (when it won't idle on its own), you can note the coolant temperature and the ECT (engine coolant temperature sensor) reading and post both up. We can see if the ECT is out of calibration (which can screw with fuel trim). It's not likely to be the issue but since it takes 10 seconds to check, it's something I'd do.
How long does it run poorly before it will idle without your assistance?