I worked in a fuel injection specialty shop for 5+ years and I've flowed and serviced many, many injectors. I also worked as both a dealership and independent mechanic, and I've used several different fuel injector cleaning systems and products. Please forgive the word-bomb I'm about to drop, but this information might be valuable to you or someone else.
The service that most dealerships offer is to connect a can of gasoline/cleaner mix to the fuel rail, disable the fuel pump, and start and idle the engine on this mix. There's a lot of different cleaners out there. Though this is called a "fuel injection cleaning," in my opinion it doesn't do much for the injectors themselves. It does help clean combustion chambers. I've found it to be beneficial on older vehicles, especially grandma cars that get puttered around town slowly, or those that burn a little oil. Probably not the case with your SSR.
Injectors usually get dirty from one of three things: "Stale" gas, baked-on external deposits, or debris. Stale gas (varnish, etc.) is most common on seasonal craft-- motorcycles, boats, jetskis, race cars, etc. They're usually run hard for a season and put away wet. Over the winter, the lighter fractions of the fuel evaporate, leaving behind waxes and heavy petroleum distillates. These foul the internal passages and valve mechanism of the injector. I used to see injectors that were either heavily fouled (reduced flow and poor spray patterns) or glued completely shut. Sometimes this could be fixed, other times it could not.
Baked-on deposits are usually caused by oil or crankcase vapors in the intake manifold. Sometimes this is the result of problems with PCV systems, but often it is caused by intake manifold design. Some late 90s/early 2000s BMWs were particularly bad about this for some reason. These deposits show up externally on the pintle of the injector and usually lead to poor spray patterns and decreased flow. A bad spray pattern can cause fuel puddling, high emissions, and even misfire if it's bad enough.
Debris is anything that won't dissolve in fuel, like sand, rust particles, whatever. Usually these are captured by the inlet sock on the fuel pump or by the main fuel filter, but sometimes they make it past and wind up in the inlet side of the injector. Sometimes they can be removed, other times they ruin the injector. The most common cases I saw were in race cars, when someone would forget to flush the bits of rubber out of the braided stainless fuel hoses they'd just made. I also saw a few fuel cells shed bits of fiber into the fuel system. On vintage fuel injected vehicles, it was not uncommon to have fuel lines shed flecks of rust into the fuel system.
What does this mean to you? If you drive your SSR fairly regularly and don't let it sit for months on end, you should be fine. The real test would be to monitor fuel trims and look for fuel being added by the PCM, but chances are if it runs OK, doesn't misfire, and isn't laying down on the top end, you're probably OK. Unless your fuel system has been modified, I highly doubt that you have much debris floating around. The LS engine is not, to my knowledge, known for baking deposits on the injectors.
The LS engines mostly use Delphi Multec 2 or Bosch injectors. The Bosch injectors are very good quality and usually very trouble free. The Delphi injectors weren't bad, but some years had a problem with the injector terminals fretting and making intermittent contact. This led to intermittent misfires that were sometimes misdiagnosed as defective injectors. If you haven't done so already, disconnect each injector's electrical connector, put a dab of silicone dielectric compound in the injector terminal, and reconnect the injector. This prevents fretting and was recommended by a GM TSB a few years back.
Unless the dealership pulls the injectors and cleans them in an ultrasonic cleaner (doubtful) and flows them on an injector flow bench, you're probably getting the miracle-in-a-can flush. They won't measure injector flow before and after, and they won't check the spray pattern for any deviations in flow. The flow-through cleaner isn't aggressive enough to remove heavy fouling and won't touch baked-on pintle deposits or debris. In some cases, the flow-through cleaning is a valid procedure, but in others it is known as the "wallet flush."
To those who say you can clean your injectors at home with an ultrasonic cleaner, you are absolutely correct-- you can, and you could well see an improvement in performance if your injectors are fouled. What most people cannot do is to determine whether the spray pattern and flow rates are correct because most people don't have a database of injector data. Internet numbers for static flow rate do NOT count, and I can't tell you how much bad injector information I've seen on the web. This is not to discourage anyone from doing it, but I want to make clear that a (good) fuel injection service company does use some specialized knowledge and equipment to do what they do.
Most reputable fuel injector companies will not only test the static (wide open) flow of an injector, but also the dynamic (cycling) flow at a given frequency and pulsewidth. This diagnoses whether the spring, electromagnetic coil, and orifice of the injector are in good working order, and I've NEVER seen a dealership do this. Not saying it doesn't happen, but I've never seen or even heard of it from a dealership. Cleaning injectors requires a very clean environment. The lab where I worked was spotless and temperature-controlled. A stray bit of rust or paint from the outside of the injector (or worse, a piece of bead-blasting media if you insist on bead blasting the outside of the injector to paint it) will clog the inlet screen of the injector and lead you on a diagnostic goose chase.
TL;DR-- If you suspect a fuel system problem and think it may be the injectors, pull them and send them in to a reputable company for service. PM me and I can recommend one if you'd like. An off-car service will probably make a small improvement in flow (probably not noticeable from the driver's seat, but noticeable on the flow bench) and get you a data sheet with flow numbers and injectors with new oring seals. I don't think it's absolutely necessary in your case, but it's your **** in the driver's seat and your call. Otherwise, I would politely decline the dealership's recommendation and instead use Techron periodically.
