This is an old revision of the document!
The throttle position sensor was a recall item on some bikes.
Go to the aprilia website and look up for recalls. It is more likely than not that it has been done. The faulty TPS has a certain number but so far I can't find the thread where this is stated.
While the TPS is beginning to die, you will have a very jerky ride with poor throttle response and lots of stalling. once it has died you won't get the bike started. Here is a sorry tale and how it was eventually fixed
https://www.apriliaforum.com/forums/showthread.php?332241-low-revs-misfire/page5&highlight=tps
The Crosfits section tells you where you can get hold of a cheap one https://www.apriliaforum.com/forums/showthread.php?343046-TPS-trail&highlight=tps