All the cars seem to have a blank just above the front of the exhaust manifold, so I guess they could be retro-fitted.
Interestingly it seems the 2.0 and the 3.2 share the same part.
All it does is run for a couple of minutes when you start up and pump fresh air into the manifold to dilute the gases until the cats warm up enough to work properly. (This is my understanding: happy to accept correction?)
Not worth fitting unless you're feeling particularly eco-friendly.