Idle rough but not all the time also engine seems

The O2 sensors seem to be fouled and acting up and are probably causing all your problems. I would start by replacing them and carefully checking the wiring to make sure it has not be damaged (e.g. burned by the exhaust system).

P0340 code means "Something" is wrong in the timing...
from CMP (Camshaft Position sensor) to the crankshaft bolt.

Very first thing, verify connectors are clean and shiny.
clear all codes, even hard codes.

1996 mustang You just go to the link I attached I'm sure you will get the solution of your problem.
Check it out once. it's instantly downloadable

seems like bad spark plugs or wires.

check /replace the fuel filter and check the fuel pump pressure before and after the bleed valve to the throttle injectors

maybe coil pac!!!

I had that problem for the longest time. I had to clean the Mass Air Flow Sensor. Very easy to get to. Go to any auto parts store and ask them for the MAFS Spray. If cleaning it doesn't work, you may need to replace the MAFS. Once again easy to replace. Make sure you put it back nice and tight.....

Sounds like low fuel pressure. i.e. fuel pump, fuel pressure regulator, or fuel filter.

Are there any problem codes!!

Check and see if the EGR valve is leaking, to check this spray water on it at idle, if the water steams off the valve is leaking and is the source of your problem, also are you sure you hooked the new DPFE sensor up right? re-check it..