sputtering

i have a 95 eclipse gs it has a sputtering problem that starts occuring around 2000 rpm and snaps out completely by 4000rpm, it doesnt do it when it s in neutral or the cluth is engaged and you rev it up. i have changed numerous items on it like spark plugs, wires, coil pack, o2 sensors, fuel filter, harmonic balancer, air filter, had my whole throttle body and fuel system cleand, and had my tranny flushed. anyone have any ideas wat might be wrong please let me know. can anyone help