@stav I have the same spec car as you and mine does the “slowing down quickly” when I don’t accelerate. I don’t think this is anything to do with what the garage as done to your car. The “slowing down quickly” is when the battery is being charged through regen. My car does this 95% of the time and I think this is helping cause the very poor mpg. There’s many roads where in previous cars I’ve been able to take my foot off the accelerator and the car will coast along. On these same roads, I now have to accelerate gently, which obviously uses more fuel. This wouldn’t be too bad if the battery then helped to lower mpg, but 95% of the time, the start-stop system (e.g. when waiting at lights/a junction) does not activate, which must be due to insufficient battery charge.
The only time the battery seems to help in anyway is when setting off, but I believe I’m using a LOT of fuel to top this battery up and it VERY rarely charges up enough to help save fuel with the start-stop system.
Whatever software/firmware they installed, I hope when mine is done I get the mpg improvement that you’ve got. What was your previous mpg figures?
Bit off topic, but I found a screw in my tyre this morning…..I think this car is cursed 😉