That is not possible. Removing the charcoal filter has a negligible effect on the vehicles performance. There is no way you would see a MPG decrease because of it. More likely, you are pushing the car a bit harder now.
You can detect right away those that are going to be shaky, and that will fall behind and those that are very hungry, and that hunger you will have to develop. You gotta create a goal for yourself whatever that may be, a short term goal and a long term goal and you gotta go after that. And if you donít see it, and if you donít believe it, who else will?