I'd pass on the TerraClean system. The MotorVac system is MUCH better for around the same price (I paid 110$ in Montreal).
I tried the Terraclean (after I had conveinced the guys at another garage that they could do it on a Volvo.) I cleaned the injectors afterwards out of the engine, they weren't very clean.
BTW: when I got my latest Mystique (I'm at my third), I had it go through a Motorvac after doing a full tuneup (with Autolite plugs), I gained an extra 100Kms per tank with the Motovac. And this was in the winter time.
I'll try to find the link to the injector cleaning on the Brickboard (the CEG for Volvo guys)