If you feel that you are outleveling content, you have the option (in "Options") to turn off XP gain. I did this at 14 & 19 in order to run all of the story arcs & badge missions at each level range, along with the scanner/safeguard missions. Once you are content that you have done everything in the level band that you want, just go back to Options & turn XP back on. While this option doesn't increase the rate that you gain INF, the longer you play level-locked, the more INF you will have earned at the end - so the effect is the same as having an option to reduce XP & raise INF rate.