I finally managed to get my car Terracleaned today at a garage called Car Make over in Wakefield Yorkshire. Mine was the first 350z he had dealt with, and he had to spend some time trying to get at the fuel hose from under the car. The actual cleaning process took about 30 mins. I was not sure what to expect, I didn't get clouds of smoke out the back, just an unusual smell from the exhaust. I was told that I should just be smelling clean air, but maybe having a sports cat changes that. Since having the process, I've noticed the car seems to rev a lot more easily, and the exhaust note seems slighty better. I haven't run any tests and I don't have a before and after emissions' print out, but the car certainly feels more responsive and livelier.