Powertrain warning light on LPG

I have a 2006 HOLDEN VZ V6EXECUTIVE 3.6L ALLOYTECH which has an aftermarket SPRINT LPG system installed (it also runs on Unleaded Petrol)Dual Fuel). ONLY when running on LPG and under load at about 2000rpm the "CHECK POWERTRAIN" warning light comes on dash and the engine runs like its dropped a few cylinders until I switch engine off, then when started the light disappears and it runs fine until under load again. ""THIS ONLY HAPPENS WHEN RUNNING ON LPG""
I had a GSCAN fault tool hooked up to it and it showed the following error codes and messages:

P0300 - Random/Multiple Cylinder Misfire Detected.
P0304 - Cylinder 4 Misfire Detected.
P0443 - Evaporative Emmission Control System Purge Solenoid Circuit.
P1632 - Immobiliser Transponder Response Distorted.

Can you give me any information as to which parts I should replace first to fix these faults?

Will it hurt the engine if I keep driving with these faults in the system?

Which Spark Plugs should I use (will NGK-R BPR7EFS-15 be ok) and the recommended Spark Plug Gap (1.1mm)?

I have recently done all repairs listed below:
Replaced the Air Filter
Cleaned MASS Sensor
Cleaned Throttle Body
Cleaned Intake Manifold & Plenum
Replaced Engine Oil + Filter
Replaced Heater Control Valve
Added Injector Cleaner to Unleaded Fuel
NONE OF THESE HAVE FIXED THE FAULTS

Today I plan to replace the Spark Plugs & Plenum/Intake Manifold Gasket and inspect the 6x Individual Coil Packs a bit closer.
ANY HELP - INFO OR ENGINE DIAGRAMS WOULD BE GREATLY APPRECIATED.

THIS ONLY HAPPENS WHEN ENGINE IS RUNNING ON "LPG" & HAS NEVER HAPPENED WHEN RUNNING ON UNLEADED PETROL