5.7 hemi rough idle and low backfire out exhaust any ideas

When we fired up our 5.7 hemi it had a pop/backfire ,found on of the injectors was stuck closed. The modern gasoline with the ethanol blends are hard on the injectors when they set . You can use your stethoscope on those to make sure they all sound the same running. If you have headers you can feel each tube after it runs for a bit to make sure they are all contributing equally.