In answer to several posts -
Ist of all lets not get confused with a working EGR, a faulty EGR and a blanked EGR
A working EGR is going to run a better MPG than a faulty one
But for best possible Performance (including eliminating flat spots and reducing turbo lag) a Blanked EGR is best, it will improve the MPG a little as well
Apart from the instant boost in performance, a blanked EGR helps to maintain the performance in the long term, because a functioning EGR contaminates the EGR housing and inlet manifold with carbon/ soot (gunge) from the exhaust, which will "choke" the engine over time, reducing performance.
If your EGR valve fails a solid blanking plate costs about £5, this wiill "fix" a faulty EGR and is cheaper than £119.99, £140 or £210, (obviously)
I've ran a blanked (completely deleted) EGR for a few years now, i know it improves performance (+ i have dyno graphs to proove it) and i know it helps the long term reliability of the engine (if only by preventing the inlet manifold getting coked/ choked up)
Many FOC members have fitted EGR blanking plates to their engines with good results