There is zero need to do a $150 service on a manual transmission. If you
haven't changed the gear oil in the last 30,000 miles, it's probably a
good idea to drain and refill it, but that should cost at most about $80
at dealer prices.
Coolant flush is a good idea if you haven't had it done in the last two
years. But all that's really required is to drain and fill the system
every two years.
As for the injector flush, I almost guarantee it'll be useless. Why does
the dealer want to do an injector service? If he suggests maintenance,
the he may as well be answering "just because I'd like you to spend $110."
If you check your owner's manual, you'll find no recommendation there to
clean the injectors, ever. I wouldn't necessarily be against using an
injector flush if the car were running poorly (misfiring) due to a clogged
injector, but the only injector flushing procedure I've seen that does
anything is the one GM recommends, using a mixture of their top engine
cleaner an gasoline.
The way the dealer is pushing these things on you, I strongly suspect
they're in "cohoots" with some chemical company. The standard deal is
that the dealer, the service advisors, and the technicians each receive a
spiff each time they use the product. My take: "The stuff is so good,
they pay us to use it." Cars don't break as much as before, and many
shops use these types of services to keep volume up to a profitable level.
Unfortunately, this is rarely done in an effort to genuinely assist the
customer more than in an effort to line the pockets of the dealership and
If you haven't mentioned the performance issue, you should do that as
well. Chances are it'll never be addressed no matter how many flushes,
etc. are done unless someone specifically investigates the cause of the
My opinion: it's time for you to find another place to have your work
done. The dealership you're taking your car to is recommending services
to benefit them, not you.