My VX sedan is dual fuel (not factory) and run perfectly on LPG all the time. It runs very badly on petrol, and seems to be chugging along on less than the allocated six cylinders when I change over. ( Yes, I know I should give him a regular run on petrol, but just haven't...)

I reckon I should at least check the injectors, and my Max Ellery workshop manual begins at the stage where the electrical connections are removed. I haven't had a serious attempt, but they don't seem to just unplug, but have a small metal bar somehow holding them on. Before I damage anything, can anyone tell me how to remove the connections so I can test the resistance of the injectors?

Or, should I just run some injector cleaner through? I tend to avoid these fix-it-in-a-can things, but maybe it's all that's needed.

If I do need to replace any injectors, it seems like quite a big job. Should I just get a Holden dealer to have a look?