It's for a metered propane system like Sgort uses on the blueflame III
But using a solenoid it could be adapted into a handle or something similar.
I know that some of them are use for a quick tuneup on turbo engines, simply add one of these for a faster blow off'ish. And some performance cars would run at 2-3bar. If the citroen could handle this pressure I don't know.
But making the "Meter" for 1x or 2x should be doable with a valve like this. And one could ofcause just increase the meter size.
If my understanding of the meter is correct it goes.
100ml meter.
14.5psi fills 100ml *
29psi fills 200ml
If you stay low on the pressure side of the meter it should work really, atleast most turbo engines should be able to toss out somewhere between 1-2.5bar on N/A parts.
If one uses a handle near the injection fitting on the tank. This valve would be relatively easy to install in that handle allowing for even cleaner builds. When you know how log it has to be open, it could be modded to the 555/556 chip. With fancontroll/injection cycles.
Pros:
Small
3/2 ports
Solenoid
12 volt
Cons:
Might not be able to handle more than 2 bar
*(14.5 psi= 1 bar)

It would look something like this I guess.
These are used on opel vectras and the picaso I recon.
The holes arent that big but shold be ok to move gasses.
**edit picture added**