During the ACT treatment there were no changes done to the original fitments of the car.
After the treatment, there was an immediate change in the performance of the car. Previously I was getting average economy of around 12 on highways (I use Chevrolet Cruze). After the treatment I immediately got the economy of 15 on the highway.
Also the turbo lag which I was getting earlier was gone after the treatment. The sound of the engine changed a bit after the treatment and the performance became smooth.
I felt like the car I was driving was in brand new condition (engine wise) even after 64,000 kms.
Overall it was a very good treatment and surely recommendable to car enthusiasts.