Hesitation

I Have An 90 Silverado 4x4 Reg Cab 350. Ive Got A Hesitation And A Code 43. Its Fine When I Apply The Gas Slow And Steady But When I Get On It , It Hesitates And Ses Light Comes On. Ive
changed Oil,air,fuel Filters Cap, Rotor,wires,plugs,tps Sensor,map Sensor,egr Valve,esc Module,ignition Coil And Module,knock Sensor,o2 Sensor,coolnt Temp,iac Valve.

Any Ideas