Your ECU is re-learning after the clean and should settle down. When I took my EGR apart and saw it had rusted for the reasons I gave in my post above I simply replaced it (after making the drain hole bigger) and it worked perfectly until I eventually sold the car. At the end of the day if your valve is shot no amount of cleaning it will work.
I applaud FOCA on his passionate essay but the original poster said he has a Euro 4 and I said the EML light will fail his MOT. I did mention that EGR blanking worked better on the Euro3.
I am sure that the expert FOCA will be able to explain how to blank the Euro 4 and guarantee the EML light will not come on and fail the MOT. I hope there is a way now (there certainly wasn't during the years I was on the forums and had my Euro 4) as this will help a lot of people.
I don't want Nate to fake the EML light from coming on to get through the MOT because this can disguise any genuine faults that may occur later....
I think its up to the individual owner to weigh up the pros/ cons and decide whether to run a plate or not,and for us to try and give the right information for him/her to choose