Has anyone added fuel additives to their cars? Which one is good?

Has anyone used fuel additives for carbon deposit cleaning? Do they work well?

Dear car enthusiasts, has anyone added a catalytic converter cleaner to the fuel tank of a 2011 manual Touran? After I added this kind of cleaner, it started emitting white smoke and the check engine light came on. Has anyone experienced this situation?

Fellow car owners, how do you clean carbon deposits from your car? Which brand of fuel additive works well? Any recommendations?

Does adding fuel additives really help clean carbon deposits? Is it a waste of money or truly effective? Let's discuss, fellow car enthusiasts.

Has anyone here used fuel additives? Do they work?

For the 2012 Kia Sportage, which one has better fuel economy, the manual or automatic transmission?

Has anyone added a seat subwoofer, and how is the effect?

Has anyone used fuel additives?

Has anyone changed tires? Which tires are good?

Hey fellow car enthusiasts, do you use fuel additives for your 3008? Which brand is good? I've never used them before.