Hi, This is my first post. My mini is at the shop for 30K service. They performed all required items, and is recommending that I also have them do a "fuel injection service" which costs an additional $110. Is this just one of those optional add ons that helps them make a buck, or is this something I actually should do at 30K, and if so, then why isn't it on the list of items required at 30K? Thanks for any input!