hotrod junkie

Converting to Edelbrock intake, ignition and carb. Engine backfires thru carb and will not start. Have gone thru all the usual trouble shooting, checked all wiring, new cam and crank sensors, checked each coil for spark, new plugs and plug wires, grounded box directly to battery, new 750 amp battery, cranking speed at 250 rpm at 11.5v, 6 lb. pressure at carb, idle screw at three turns, fuel is being injected when throttle depressed, compression is 180 to 190 psi at each cylinder.
Does anyone have any ideas?