X-man, if your wheels already have TPMS sensors and they have just gone bad, then all you need are replacement sensors because the stems can be re-used. If, on the other hand, you have winter tires or spares that don't have TPMS sensors at all, then you'll need the sensor and the proper length stem to go with it. I'll try to find out the right stem for the QP and post it...
2013 Maserati GT-MC, Bianco Eldorado/Nero
FD Drive By Wire
(Traded) 2009 Maserati QP, Grigio Granito/Nero
Larini X-pipe, Larini Valved Mufflers, FD Drive By Wire, 20" Neptunes, GTS Concave Grill, Ultimate Race Pedals