OK this is whats happening. I have this 02 impala. And if you have the slightest knowledge of these cars they are known to have power. Now my car is not the case. When im at the light and the light changes everyone is way ahead of me and i can fell like my car is trying really hard to build p speed. Its not transmission problem cause it shifts PERFECTLY.when i reach 25 and then at 50 then so on. Now according to most reviews of the car it should be getting about 23-26 in city and about 32 on highway. Here again its not so with this car. I get about 15 at the most without ac on. I've put a fuel injector cleaner in and i dont even know if it helped. Do you think that it could be a clogged catylic convertor, spark plugs, fuel filter. Please just looking for a solution. P.S. ran computer scaner and no codes came up.