I's not the MAF sensor as I had a new one 3 months ago to try and cure it. You can unplug the MAF and the ECU will revert to preset values and will run more or less OK, but the problem is still there! It's interesting that the problem is not there on cold start up, which to me does point to a fuel mixture. Is the pressure regulator on the fuel filter electrically operated? Think I'll change mine anyway as it's not expensive, easy to do and can only be beneficial.