An mot tester once failed my van for " a vehicle fitted with a dpf making to much smoke".
I was very surprised it being a 2004 pre dpf so I pointed out the error of his ways it had passed its emmisions during the test he quickly retested it and passed it at my threat of reporting his...
Buy your self a new blue solenoid then and swop it out then. Check it's actually got gas in the tank it will have a pressure gauge on the tank.
It's a 5 minute job to swop it out
I'm outa London I mean on the very edge country side proper here. But inside the ulez tax zone. I'm sure I could sell up BUT my work is here my elderly mother is 10 mins away we look after her. My boys who will never be able to afford to rent here let alone buy here are settled in there jobs...
Mpg is pretty much the same as on petrol to be honest I stopped checking soon after I got use to the car and just filled it up with lpg when it needed it. Starts on petrol switches over when it's ready and it's never missed a beat.
Conversion was done by the previous owner at a then registered...
So finally made the hard decision to part with my fullfat dream car. I will get it back to mine where it will get a full valet and check over its been stored at my mates place outside the ulez iv been driving out in my ulez car using the fullfat outside the zone then swopping again to come home...
Yes the steering column lock module will need to be sorted BUT to be honest you have change the wrong part to cure your issue.
It's the lower steering column shaft that causes your problem it's a well know failure item on all d3 d4 sport models.
Iv change mine on my sport an after market item...
Try sitting on each seat in turn jump up and down in the seat.....seriously you mite feel a fool but it sometimes works. Without a gap tool you will not be able to turn it off but as you say "it goes off then on" try the seat trick