1995 Chevy Lumina Feels liking stalling at high speed accel

When driving at interstate speeds and trying to accelerate my car feels like its stalling. If I hit the gas hard it does just fine. Light acceleration however causes it to shake and get really sluggish not picking up much speed at all. For instance at 70 with the cruise set it runs great until I go up a hill. Then the shaking starts almost like its starving for gas. I use the reference "like when you gas a weed eater too hard and it doesnt rev up it just floods and sputters for a sec". I've changed fuel filter spark plugs, wires and tried fuel system cleaner. And Ideas?