What would make my 4.0 Idle OK,but backfire when I accelerate?

Here is what i've done so far...

Replaced new,Distributor,cap,wires,coil,tps,crank sensor,map sensor,and control module.(used):banghead:

Any help would be appriciated,Thank you...

How about a set of plugs?

Also, does it backfire under a load but run smoothly when revving without a load or at high rpms?

You might also want to clean the inside of the intake, carbon fouling there can cause an issue. How many miles?