ATX-Iroc

my engine stutters and shakes at part throttle unless its at very light load( 50 mph in od). If i really get into the pedal it smooths out until it shifts and brings the rpms back down. I'm really stumped on this one. I've checked all my plugs, my wires, checked the cap and rotor, sprayed carb cleaner around all my vacuum ports and gasket surfaces to check for vacuum leaks and found none. one thing i will add is that towards the firewall it sounds like a bilge pump (bloop bloop bloop). If you have any suggestions shout em out i really need help on this one