When I was doing the thermostat replacement I noticed that the EGR valve had started to coke up quite heavily again. Considering the time and mileage since I had cleaned it, I was quite surprised and concerned.
I did some reading around on bimmerforums.co.uk, and the general consensus is to bypass the valve altogether. There is an extensive write up on the forum and a considerable amount who have had the valve bypass for several thousand miles without problems.
Just to show how quickly the build up forms in the EGR, here is a picture from my EGR Cleanout post I wrote in September showing the valve freshly cleaned.
Now here's two photos just 2-3 months later, around 2000 miles.
Already it is looking a lot worse.
It is quite easy to bypass the EGR valve, as I will now explain.
Remove the engine plastics until the EGR valve is revealed, then locate the small vacuum pipe on the right hand side and pull it off.
I then rummaged through a tin of assorted bolts and set screws until I found one about the right size to plug the vacuum pipe just removed. I used a bolt so that I could cut the thread off and just use the smooth shank (to avoid splitting the pipe).
Next I found something to cover up the tube on the EGR valve. For this I used a bit of silicone hose that was a real tight fit. Then plugged it with another bolt cut down.
With everything now plugged, I took the EGR valve off and gave it another clean in a bath of petrol. It's a messy job but the results were good.
Finally I just replaced the EGR valve, ensured both plugs were in tight, then cable tied the two together so that neither flapped around and could easily be located if I wanted to re-enable the EGR valve.
So far I've noticed no adverse effects, only positive ones. The car seems to rev more freely and pulls slightly better. I will update in a few months if there is any developments.