The injected KTM’s have the worlds smallest fuel filter.
It resides in the spigot that the fuel hose attaches to the injector rail assembly.
[attachment=3001]KTMFuelFilterLocation.jpg[/attachment]
Below is the KTM schematic of the associated parts
[attachment=3002]KTMFuelFilter.pdf[/attachment]
This is the filter, hard to find if you don’t know where to look
[attachment=3003]KTMFuelFilter.jpg[/attachment]
The easiest way to replace the filter is to disconnect the fuel line at the quick connector and undo the screw that holds the elbow to the fuel rail. There is an ‘O’ ring that seals the elbow to the fuel rail. It may stay in the fuel rail, it is easier to take it out and put it onto the elbow for assembly.
Cut the existing non-replaceable hose clamp off the fuel hose and pull the hose off the elbow spigot.
The filter is that tiny black thing you see inside the spigot ( you may need your reading glasses ), remove with finger nail or small screw driver it just pulls out.
Push in new filter, push hose back onto spigot and replace hose clamp with a removeable one. ( if you ever need to do this on the trail the re-useable clamp will make life easier )
Push elbow back into the fuel rail being careful with the ‘O’ ring and insert retaining screw.
Re-connect fuel quick release and your good to go.
It may be easier to remove the fuel tank for this, it may also depend on what model you have 
Keep everything as clean as possible as it takes 3/10 of f*** all to clog this filter.
Hope this all helps 
Adam.