1996 Lincoln Continental 4.6 32 valve surges

I have a 1996 4.6 32 valve Anniversary addition Lincoln Continental. When the weather is cold or the engine is cold it will accelerate normal under full throttle during the warm weather once the car warms up it will surge under heavy throttle and slows down under full throttle. I have replaced fuel filter and spark plugs with no improvement.I have added fuel injector cleaner today but car has not been driven enough yet to show any results. Before I nickle and dime myself by buying parts that I do not need do you have any suggestions what may be causing this?