Sounds like a sticky EGR valve to me. Just give me a sec to copy and paste another post of mine here to help you...
here it is:
How to clean a sticky EGR valve
This article pertains to all models with the OBD-I Northstar 4.6L V8.
The symptoms of a sticky EGR valve are surging while trying to keep the throttle steady (not to be confused with surging at idle), and
code P036 (E036). Although it is possible to have a sticky valve with no code (that's how mine was).
First of all, don't do this job when the engine is hot. You WILL burn yourself. Your first task is finding the Exhaust Gas Recirculation (EGR) valve.
It is located underneath the spark plug wire cover near the rear bank of the engine. You will have to move the spark plug wire cover, you
don't have to completely take it off. Just lift it up and lay it sideways on top of the engine.
Now you need to unbolt the EGR valve. To do this, you will need a ratchet with an extension, and a 10mm socket.
Once you know the bolts are unscrewed all the way, don't try to remove them. Instead remove the whole EGR valve with the bolts still in the holes.
This will prevent you from dropping and loosing the bolts.
On the bottom of the valve you will see two holes, one that is plugged with what appears to be a screw and one that is open.
The screw like object is the valve. You should be able to press it in easily and when you let it go, it should close itself again (it's spring loaded).
The one I was working with was sticking in the closed position.
To clean the valve, simply spray carborator cleaner on and in the valve and wipe the dirt off with a cloth. Be very careful not to get it into
the canister, as the carb cleaner is a very powerful deturgent that will eat away the insulation on the windings in the sensor.
The following picture shows what you should not
The picture below on the other hand shows the right way.
Once you're all done cleaning the valve, you can reuse the gasket and put it all back together. Just make sure that when you put the
spark plug wire cover back into place that it clears the water pump belt.
What you have just done, should take care of your P036 (also E036) code. You can go into diagnostics mode and clear the code. If by chance it
didn't take care of the code (the code comes back after clearing it and going for a test drive), repeat the process.
If you can't get the code to go away, no matter how many times you clean the valve, replace the valve.