1999 Nissan Altima REVVING PROBLEM

Sir, My name is Valerino and I have a 1999 Nissan Altima GXE Sedan. When I press and hold my accelerator down, The engine hesitate to rev to the fullest. By that I mean: The sound goes up and down as I press and hold the accelerator down. It behaves as if I am the one releasing and pressing the accelerator pedal, but I just held it down actually. I manage to clean the injectors but the problem won't go. Please help me out. Thank you Sir!