A3 1.8T (x reg) EMS light/occasional judder at idle/loss of acceleration

[tusken]

I was wondering if anyone can help me with some issues im having. Im desperately trying to avoid spending a fortune on garages diagnosing and changing all sorts of parts which doesnt fix the problem.

Initially the problem was just the the EMS light went on and off intermittently. The car still drove ok. I did get an Audi dealer to check it with vag.com and the diagnosis was change the MAF, and also a faulty breather pipe.

Having read several forums and seeing that changing the Maf rarely fixed this type of problem, I did nothing for a while. I then started to get an alarming judder on starting the car up, but this would only happen about once per month. The car would have no power whatsoever and would basically limp along terribly, but eventually it would clear on that same journey, and be perfectly ok for about a month, until the same thing would happen again. (by this time the EMS light would be on permanently)

i opted on advice for changing the pre-cat lambda sensor. Due to disconnecting the battery the EMS light went off, and the car was fine for one month. Then on friday the EMS light came back on, but still was driving fine. Then on sunday the dreaded monthly juddering was back. so i have several questions please:

1. could this juddering be caused by the maf, as it does it at idle? i wouldnt have thought so.

2.Is a breather pipe a vacuum hose - i have the audi part number if that would help identify it - could that cause the juddering and the loss of power - as its so occasional?

3. I have read that the judder could be a faulty coil pack - but could it be this as it only happens once per month?

4. clean throttle/leads - i dont think this would help as the judder is once per month and the rest of the time its as smooth as anything.

5. could it be th throttle sensor or motor?

thanks