It also stutters at 30 mph when in fourth. The revs are definately not too low. In my opinion I think it is to do with the management system not adding enough fuel it that particular rev/mph. It would be interesting to see what a remap would achieve.
I find just altering throttle just slightly works a treat.
by the way, yes the van is slow but it has less to go wrong. I brought it as a work horse and it does the job. Starts first time and has ever let me down. My mate has the same engine in a Ducato! now that is slow! he says my van is very quick compared to his.
I too have this fault on my 2001 1.9D non turbo Cargo. I have considered every possiblity have read the numerous threads on this subject on the forum and still find I'm stumped. I have though learned to live with it and find that if I change up to fourth at any speed above 32 MPH the problem isn't so pronounced, also I am a persistent clutch coverer and have found that even the slightest pressure on the clutch pedal makes the problem worse, hence a long overdue change in driving technique for me
I tend to stay in fourth for as short a time as possible unless on an incline but find that booting it uphill also tends to lessen the problem, still intrigued.