It's called the smoke container. In the config file you will see "smoke1, smoke2, smoke3 etc. But if you delete the lot you might come up with an error.
I have not tried this but it might be better to leave the smoke containers in place and just delete the values in each tag or make them all zero.
Make sure you clone the loco before you start and work on the clone. That way if it doesn't work you still have the original loco.
Bill69