I could be wrong but it sure sounds to me as though you could have been
misinterpreting excellent advice as an attempt to rip you off. If the
injectors are relatively low hours, maybe it was an anomaly. However, if
they looked at your filters (first thing to check and relatively low cost)
and other things and saw an engine that hadn't had much preventative care,
it would be very reasonable to suggest that the time it was starting to show
problems would be a good time to make everything right.

If they had just done the minimum and gotten you off their dock only to be
having more problems 50 miles later, what would you have been posting on
your web site?

--
Roger Long