I have been looking into this for some time now...
You should speak to mrshin (forum member) as he is currently running / experimenting with a LPG injection setup.
There have been several mobs (One who was really doing well called Liquiphase - try googling it up) who have spent a fair amount of time developing this, but they all seem to disappear when they run out of funds.
I am currently running one of my vehicles on a GasResearch LPG setup (A 3T-GTE turbo powered TA-22) & works quite well. The larger sized throttle body is probably the biggest benefit, the total lack of throttle response is probably the biggest downfall.
I am waiting to hear how mrshin is going with his setup, & when has it sorted, will look at doing something similar.
You should really look into direct LPG injection.. one example why.. the cooling effect of injecting raw / unconverted LPG into the engine is very useful, especially if you are wanting to run higher boost.