those fironi diffs are more like this Xray Active Diff than a Torsen dif.
http://www.teamxray.com/teamxray/new...a4491ea8139be7
The Xrays difs are tough and hold up well, I would expect the same from the Fironi. Xray only make them for the front dif though. Nothings available for a center diff. Not sure why you would want one in the center to be honest. If you put one in the front it basically locks the diff uner power and makes it easier to pull hard out of corners, but opens up again off power and lets the car corner normally. Good for smooth tracks without alot of traction. Not so good for high grip tracks or very bumpy rutted tracks.