yes, none are serviceable, but there is an injector relief valve inside where the injector mounts. It has seals and other misc parts that may be affected by a harsh cleaner.
Also under one of the covers (where the injector boost solenoid is there is a thin screen that can get dirty, not sure if carb cleaner will hurt that, its made of either aluminum or steel, not sure but it is fragile.
When i worked for cat we usually did not go into any of those components trying to rebuild or repair them, it was more cost effective when we just verified they were faulty and replaced them.
I used Carb Cleaner. Are there internal pieces in the injector assembly other than the removable injectors and pressure switch?
my first question to you about cleaning the injector assy and throttle body is "what did you use to clean it with?"
Using the wrong cleaner can damage parts internally and cause all sorts of problems.
Absolute 'no no's' are carb cleaner and brake cleaner, those cleaners are way too caustic and will eat up the rubber & plastic parts inside the injector body housing.
I use either an electric motor cleaner or a mild parts solvent and then blow dry with compressed air.