I have heard of people putting ATF in where the spark plugs are to restore compression when there car has problems fluiding. I also heard that it breaks down carbon. My car isn't fluiding but would it be a good idea to use it anyway just to break down the carbon?

 

No.

 

use marvel mystery oil, but read this whole post first https://www.rx7club.com/showthread.p...hreadid=281207

 

Or MOPAR Combustion chamber conditioned
Or deep creep

 

Personally, I have had excellent success with adding a full can of Seafoam to about 1/8 tank of gas. It might smoke a little, but I felt a huge difference after about 5 miles of hard driving...