I'm guessing what your saying is that it doesn't idle properly so you're going to change the ECU?
its like a human !! bare wi mi if the bones in the leg are faultless muscles tendens skins blood nerves and what ever else lol all in good workin order but you still cant walk what holding the legs back

?? the brain maybe ....mind made up fo me the ecu from mk3 vbuds were not upto job simple as ....
I'm guessing your saying that if your legs are fine but don't work it's your brains fault... also you think the MK3 ECU is sh!t...
You haven't even said what you have done or what car it is, but i be changing the ECU doesn't solve it....