Let's do this one step at a time.
You may have to take the plastic plenum chamber off to do this. I haven't seen a Zetec so get a Haynes manual and read.
On the EGR valve there is a small vacuum line. The EGR valve is shaped like a flying saucer on it's side hooked to a chunk of metal and has a metal tube the size of your finger going down to the exhaust manifold. Remove the line and plug it with something that won't suck inside. Disconnect the battery for awhile to reset the computer.
Now keep notes on how it runs from cold to hot and at idle to driving around. Post your results and then we can check something else.
And look at that tube while your at it. There should be two hoses connected to it. See if you can get your hand down there.
