The key here is the comparison between before and after. Take the EPA/ECE fuel test results. We all know they are pish because they are in a lab - thats not the point of them. They are there to provide a consistent comparison from one car to the next. Given the testing methods used the comparison can be seen as valid or not for the rest of us in Ecomodder land as we don't drive "normal"
Assuming the OP uses the same car and the same method of measuring and the same prep and the same method then I would suggest it is at least stage 1 in testing. If he/she/it details the testing method with photos etc. and comes up with results then we can start. Then others can follow up and redo the tests in the same way.
<opinion>
I don't think that magnets will make a difference as I have tapped earlier, but provable results make the difference between "hey I got this outcome with super-x" vs "super-x is a proven improvement.
I have an open mind on it.
</opinion>
The ball now lies in the OP's court.