Newbie here. Have not done intro to forum yet. 1999, 4.6L, Auto Trans. Car is new to me. At heavy acceleration or WOT, it runs great. With light load (going up a long moderate incline) it hesitates as if bogging down and needing more power. It will eventually downshift to a lower gear, accelerate, & upshift to the next gear. I added some injector cleaner & drove about 100 miles. It still does it. It also idles quite rough. (sometimes enough the tachometer shows it) All comments appreciated. Ezre