I'm curious to know, if it creates more power and uses less fuel, why didn't MG Rover do it in the first place
The only cars I could see that would be worth doing for any real noticeable difference would be the ZT turbo's.
If it makes the car accelerate quicker surely that would cost more fuel
Most folk that have had a remap do say the car is better afterwards.
I was tempted to increase my ZT 160 to 200BHP with a remap but it was always plenty quick enough for me so I never bothered.
As they say you pays your money you takes your choice.