my 95 Altima 5-speed standard is in great shape but recently it lacks power

Thanks for your response. I have no check engine lights on at this time. i changed EGR, Mast Airflow Sensor,fuel pressure regulator and I still have that nasty dragging/hesitation and when the excelarator pedal is flat to the floor I feel resistence. I took the catalytic converter off and took to the Auto Parts store to get me a new onebut they seem to think it looks good. There is no break down of the mesh etc. I'm puzzle!!