Terraclean definitely works. My mechanic did it on our 2.4JTDM Sportwagon before we deleted the EGR. We inspected the inlet manifold with an endoscope camera before and after the treatment and it was far cleaner with shiny metal showing afterwards. In my opinion there is no point doing an EGR delete without doing this first. Why leave all that crap in there? I expect the system to stay much cleaner without the EGR. The turbo boost gauge showed the turbo was picking up sooner afterwards and the car feels more responsive. I for one, am not going to allow my engine to be ruined by a flawed piece of technology.
2004 GT 3.2 V6, Grigio Stromboli
2008 159 ti 2.4 JTDM Sportwagon, Grigio Stromboli
1989 75 3 litre V6, black
1988 75 3 litre, red, (son's car now)
2000 156 TS 2 litre, Cosmos Blue, (daughter's car)