Along with the obvious questions above, it might be advantageous to say why you were convinced that an EGR valve was key to your problem, originally. Is it just the limp mode thing that you mentioned, or was there something else (anything about the symptoms, basically).
Also, do you have any chance of getting the codes read? Codes could be a very good clue, and without them it might be a bit of a scattergun approach.
Is the car the 2008 you mention in your thumbnail? And how many miles?