the crank and cam sensors do play a part with the fuel delivery but not directly.
the ECM monitors those signals along with the TPS and TB position, map sensor and O2 sensor, basically monitoring the air/fuel mixture and send signals to an LPG drive unit module which controls the LPG injector telling it how much or less fuel the engine needs.
Early models had an external LPG driver module and later on during the late tier2 or early tier3 versions they incorporated it into the ECM.
what is your serial number? i might can tell you what should be in yours