As nobody else has replied, I'll give it a go. I have no idea what a deg 104 is but assume it is a lambda controller of some sort. LPG for the Australian market is often the same as we get over here but with a different name and firmware.
The easiest way to check if the stepper is working as it should, refit your manual valve and have the stepper connected to the wires but not in the pipe so you can watch it and see what it does. With the engine running and warmed up, screw the manual valve in to make the mixture lean and you should see the stepper open up to try to correct the lean mixture. Screw the manual valve out to make the mixture rich and the stepper should close up to try to correct. If it doesn't it may be that you have a faulty lambda sensor (O2 sensor), or damaged wiring to it, so it is not giving a signal to the controller. In this case no signal will be seen by the controller as a lean mixture so it is likely that the stepper will open up fully and stay there. This assumes that the stepper you have got is the correct one for your controller but I will admit that most of the systems you have down under do seem to be rebadged AEB units so I would have thought it would be correct.
You may get more response by posting in the Having Problems forum, this one tends to be used mainly for announcements of news from Australia and New Zealand and isn't somewhere that gets too many visits. A problem is a problem no matter where in the world you are.
'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....
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