There is absolutely NOTHING wrong with that and is completely NORMAL. It is only because you have an accuarte gauge that you can see the temps fluctuation up and down when stationary and as the fans come in and go out. If you look at your OE Ford gauge, you will find that it never strays outside of "norm" when this is happening .

You're wasting your time and money trying to cure a problem that isn't there . IF the temps were not held down by the fans coming in THEN worry .