Nico,
So you have two issues here...
Th first one is that you will have difficulty knowing what the impedance is near the matching network because your measuring system is affecting the results. That was the point of my previous post.
The second is that even if you knew precisely what impedance you are trying to match inductors and capacitors at 916 MHz. will not have the same values as they do at lower frequencies. An inductor will have series resistance that increases with frequency and parallel capacitance. A capacitor will have lead inductance. So you need to purchase components that have been characterized at 900 MHz.
Roger Need