TPS = throttle position sensor
Basically, it's a potentiostat (a volume control) that tells the FI how far open the throttle is, so the FI can determine how much gas to squirt in. Setting the TPS is analagous to setting the volume on a stereo, but you measure voltage instead of decibels. The TPS itself is just a plate screwed to the top of one of the throttle bodies. It's on the R/H side, has 'Marelli' stamed on top and has three wires coming out of if.
FI tune-up procedures are scattered here and there:
For the Tonti frames see here. There are a few differences though- On spine frames, the TPS is on the R/H side.
Here's a thread that has lot's of info in it (too much maybe?). It's aimed to PCIII owners, but it's applicable to standard TPS adjustments.
Basically- measure voltage across two of the three wires (the outer wires, I think) with the bike on, but not running. You'll have to pull the rubber boot back to get to the connector and I use a small gauge copper wire to stuff into the connector without ever disconnecting it. It should read in the 5-575 mV range (make a note). Gently loosen the two top star bolts on the TPS and slowly twist it one way then the other- the 500 mV reading will change up and down. Rotate the TPS so it's about 10 mV higher than it was when you started, tighten the star nuts and take the bike for a ride. Since this is a rough dial-in, don't bother with disconnecting the linkage et. al. Also, if you have a twinmax or similar carb balancer, you can balance the TB's with the white knob between the two TBs (bike running, of course).
If you're not comfortable doing it yourself, any shop should be able to set it in a few minutes. Maybe watch them, so you can do it yourself later.
Hope that helps.
Jason