Where does the PC mount on a 2005 R1

I bought my R1 used a couple of months ago and the guy said it had a PC3. I took his word for it and it does seem to run great but then again, it's my first R1 and even stock they are pretty strong.

So...where would a PC3 be mounted? Under the seat? In the tail? Somewhere else?

If under the seat or in the tail, then I got screwed because there isn't one there.