Unblock diesel Filter 307 2.0hdi?

Hi, i got the message unblock dieseal filter on my 307 about a month ago, sent it in for a full service and a code read, they told me the particular filter was blocked and the air flow meter faulty. So..I had a look around certain websites for advice, new particular filter Around £400 but did read it could be cleaned... so i ramped up the car and after about An hour i had it off, mine filter is a constant long one (doesnt break into 2 parts) none the less i got some washing up liquid and a power washer and begin the task off cleaning it out...
did this about 8-10 times and the black water that came out was un-believable!! once clean water began to flow through i let it dry and put it back onto the car...JOB DONE it solved the problem and runs 100 times better than before, however i still had the issue of it not going over 3000rpm for about 5 mins each morning so replaced the airflow meter (£50) but still the rpm problems remains. I now have no warning lights etc and no error messages so i know the particulte filter is now fine and also the air flow meter...can anyone advice what this issue maybe? personally i think its the computer needing a reset to tell it its solved but surely i would still have warning lights? After about 5 mins driving in the morn normal power returns and its fantastic pulls great smooth acceleration etc just those first five minutes when its restricted. i must ass cleaning the particular filter is not a job for the faint hearted however if you do feel confident enought i would strongly reccommend it as it has saved me hundreds and of course i would be happy toi give guidance of the procedure knowlesleigh at hotmail.com. any responces would be much appriciated :) thankyou all...