1975, plymouth duster, 225 cid super six., 2bbl, AT

I own a 1975 Plymouth duster with a slant super six, I have replaced fuel line and put a electric fuel pump and regulator and have 4psi fuel pressure, replaced electronic ecu and new wiring for same, rebuilt carb 2bbl, new ballist resistor, new distibitor, new plugs and wires, timing is correct, vac. 20 and rpm’s are right. hard starting when cold but starts every time hot, idles great, runs great driving on flat ground but to drive up a hill and it will die every time. I am stumped???