Surely that will cause a misfire condition..
What does it rev like?
Any hesitation?
That's true if you know how to spot a missfire.. depending on how open the injector is..
It did seem to rev OK, but to be honest the engine is quiet anyway so it could well have had a missfire without me noticing. It switched to lpg after half a mile and then all seemed ok.
Is it possible to disable each injector in turn to see if that stops the smoke?