Title says it all.
Living in Europe corresponds to high gas prices, so i was wondering if an ECU remapping might save some money in the long term. Also… are there any negative impacts on the engine or other parts that should be put in consideration?
Nope
Automakers spend tens of millions tweaking the code in the ECU, no amateur tuner has any special magic sauce to defy the laws of physics.
Keep in mind that tampering with emissions equipment voids warranty and typically violates air pollution regulations (it does here in the US).
Factory tunes need to compile with emissions regulations so with custom tune which doesn’t compile with them you might save some amount of fuel. Basically it’s illegal but there isn’t really a way to test for example NOx easily, that’s why it took so long to catch vw with dieselgate.