replaced plugs & ignition wires vehicle now idles ruff and under load reduces

I tried that and still having the same results. Idles ruff out of gear and when I place in drive or reverse takes about two mins of driving time to get up to approx. 25mph than it acts little more normal. Also when it does pick up speed it shifts HARD. When it does get up to normal speeds and approaching even a slight incline it starts to lose power/speed.