more fuel for a over fueled engine???
forget the propane or turning up the pump until you can get rid of the black smoke under load.
ie: you need more air......
once you install a pyro meter. to get your base line.
install a stock sized turbo. if your engine never came with one, size it appropriatly.
review your new pyro temps.
then start adding more fuel, injection timing, propane, new cam(s), change compression, ect.
remember the propane is to help burn the fuel that doesn't atomize properly.
any black smoke you see is just wasted fuel.