Golf MK4 1.6 engine softly shakes only when standing &on LPG

[77771234]

Hi Everyone.

I would sincerely appreciate your help. Got a Golf MK4 1.6 Petrol & LPG. Used normally for work. Runs perfectly quite on Petrol and LPG but when I am on LPG and stopped (not moving at all) I can feel soft slight shakings transmitted to the cabin by the engine. The shakings are almost un-recongisable still if you are careful you can feel them when stop at a traffic light or so. When the car is on LPG and moving it does not transmit any shakings. While when running in petrol no shaking whatsoever whether while moving or stopped. What could be the issue? Could it be its old LPG system or some air out flow? Have changed the spark plugs recently as well and still the same. Like said it runs perfectly well without any problem, just when careful and the car is stopped you can notice some shaking transmitted to the cabin from the engine which apparently doesnt run as smoothly on LPG. Would appreciate any opinion or suggestion. Thank you in advance.

[77771234]

Thank you man. I hope as well, it is nothing to worry about.

BTW, was talking to a friend and he was suggesting that it could be a vacuum leak and as such it is felt much more on lpg rather than petrol. Could that be a reason for the shaking?