1989 626 cut out at 4000rpm

I've had this problem for awhile. When trying to merge onto a freeway, my engine will cut out and sputter at about 4000 rpm. Also if I floor the gas pedal it will stall and stumble until I slowly back off then it will recover. I have changed the coil, distributor twice, rotor, cap, fuel filter, checked the fuel pressure regulator control valve, the air flow meter, vdv. I am stumped. Thanks for any ideas. Greg