As previously stated the Mass Airflow Sensor is the number one suspect.........unplug it and if it goes better then there's the problem. You can try and clean it with isopropyl alcohol but getting a new one is a better idea........not a cheap one from ebay.
Your EGR valve could also be blocked and is also a major headache on these engines although it is a quick 5 minute job to get it off, clean the whole thing with carb cleaner (including vent pipes) and put it back on. My JTD 130 wouildn't even overtake trucks on the motorway with the EGR blocked and MAF knackered. I pulled out enough carbon to melt the north pole!
Try changing the fuel filter
There are loads of guides on here on how to do the above but if you get stuck drop me a PM.