Does anyone use fuel additives like Techron. I had my Mini S in for a 15k oil change last week. The service guy asked if I wanted the full 15k service. The oil change is $125 so I asked how much for the full service and what do I get. Well I get a bottle of injector cleaner, a new cabin filter and they look for error codes $400. I turned it down but the fact Mini recomends injector cleaner. Techron comes highly reccomended on the Mini site. The last it was mentioned on this site was 2 years ago. Claims to keep carbon down and keep the injectors atomizing correctly and even cure hard starting. Has anyone used it and noticed a difference?