id gas it all the way although the initial layout is a lot more to gas it in roughly 4 years time the money you save on fuel will be twice as much as you spent on the conversion plus if its done by a registered gas instalation garage they usualy give 3 years warranty and if you decide to sell the vehicle again theres no stopping you getting the gas system removed by the garage and put in the new one usualy at the £400 mark
whereas the remapping can cause allsorts of faults if not done properly
regards john