The lpg system is a factory fitted vialle system. It has four injectors under the inlet manifold, which squirt cold lpg direct into the engine just like petrol. The pump is in the tank.
The piggy back system takes the petrol trims and uses these for the
I have removed most of the lpg system, fixed the holes in the inlet manifold.
Maybe the vialle installation instructions will point the way ahead? Lpg forums maybe a good way forward.
Ian