First I would question whoever made the recommendation. If it was your local quick oil change place, or chain outfit, the recommendation can be called a wallet flush.
Unless you are having some sort of problem there should be no reason for a fuel injection service. Even if you are having a problem, don't start with a flush or some sort of general service, Find out what the problem is and work from there.
Since you have a manual transmission, You don't need it serviced until more like 75,000 miles and then you don't get a flush it is just a fluid change. Even that could be considered overkill.