Mt_high

Hi i bought a car last year and it has now 30000 miles on it but last couple months i have been experiencing a slight hesitation accelerating my car. The engine is not giving proper thrust since i can feel it. i went to honda dealer several times but nobody understand what i am saying rather they says engine is ok. i thought it might be because of bad oil and i changed it. it did not work. then one of my friend told me about the transmission fluid so i changed it last month along with brake fluid. In the beginning it feels like the problem the solved but after 1000 miles on it starts again. last week i meet a guy who told me he is a self taught mechanic and i asked him about my problem, his answer is because of the engine clogged. He suggested me to use those fuel injector cleaner and i did it but still having the same problem. i used lucas fuel cleaner injector. Is this is really the engine clogged problem? and at what miles we should use those kind of product? this is my first car and really doesn't know anything about auto parts. Can anyone be a great help?