Thanks for the info. I think carbon build up is a fact of life, my thought is it would be better to start early rather than after it's built up and comes out in a higher concetration maybe even chunks. In my case I wanted to because of the possible carbon build up in the cylinders/pistons. As I explained in a different thread, I may have degraded rings cause by carbon build up when AFM is on, which is why GM installed the AFM deflector last week.