I've got a 2010 Opel corsa d 1.2 GplTech, now with about 84000 km. The car seems fine, does not consume excessively and even the mechanic said this January that it feels solid.
However, when I'm on LPG and go on partial throttle I hear a low-pitch 'humming' kind of a low note, must be few hundred Hz. This does not happen if I'm running on gas (well, technically the gas is the other, anyway the regular one) so I believe it should be somewhere in the LPG circuit.
Any clue about the possible cause?