I know that the throttle body and fuel injectors need cleaning pretty badly, and I changed an 02 sensor the other day but why all of a sudden is the engine sputtering and losing power when the CEL is off but the second it comes on it seems to run fine. I have the pedal floored and the RPMs are barely over 2500 while its sputtering and if I stop the car shuts off and wont start again for several attempts. But if I stop while the CEL is lit then it won't sputter and die. What is going on?? I'm going to have the TB and FI's cleaned as soon as possible but is something else going on here? Also there's a lot of grey smoke (carbon i guess) behind me when I'm driving whilst its sputtering but seems to not release as much when the CEL light kicks in and it smooths out. Also had a full tune up done the other day, could it be a complication from that?