I used injector cleaner of LM after i swapped the engine, the injectors seemed to be black especially the tips and the filters were clogged to some extend but the condition inside the injector ? , u never know
I added the injector cleaner with 20 litres of petrol and experienced amazing results , the engine start up time reduced to minimum and smooth ideal , the acc. became better as well
I opened the injectors after 100 km to see either they were clean or not and trust me , the tip and filters were all clean
The thing is that such products help u when there is a need of help , i used them cuz i swapped the engine clue-less of the history
If u have a regularly maintained car then they wont show too much noticeable positive response
And if they don't show response , it doesn't mean that ur money is wasted , it pretty much makes sure that they're wasn't any need of it as its working fine
P.S Mobil and LM and 3M are trusted brands if u get the original product , u cant straight away jump to the conclusion if u don't feel a difference, maybe the difference in in-noticeable and may have a better long lasting effect or ur setup did not require the product u used