Don't put anything with PTFE in it in your engine!

That is the active ingredient in most of these 'miracle" products and it is basically Teflon. Dupont, maker of Teflon actually was sued by Slick 50 because they were telling people not to put Teflon products in their i.c. engines. Amazingly, the courts ruled that Dupont had to stop telling people not to use the product that they themselves developed.

http://skepdic.com/slick50.html

http://www.msgroup.org/TIP043.html