Simply boring out a worn engine will not increase its needs for more propane. The actual increase in total displacement is insignificant insofar as the fuel system is concerned.
But, the engine may not be timed correctly regarding the timing belt. One tooth off and the engine will barely run.
An issue I ran into on a 4G63 in a Mitsubishi forklift was that the vacuum advance unit on the distributor was packed completely full of dirt and debris to the point that the vacuum advance was not working at all. So you want to double check that the vacuum advance is working.