There is no scheduled maintenance that I know of. It depends on fuel quality and use. I have run DD's 165 and 175k w/o injector service.

When they are serviced is is usually cleaning on or off the car. If done off the car, they are checked for flow rate and pattern. On the car is with a fuel additive or may be plumbed up to a machine to inject cleaning solution.

If one or more are not working well, it will normally throw a code. No harm in getting them cleaned but may not be your problem.

I wonder if there may be other issues like tires or alignment, plugged converter ect. Also, does the transmission shift smoothly through all gears and lock up at cruise? Any aero changes?