My 02 VW Jetta TDI is running rough. I was driving down the road and lost power and rpms. I could not get over 1000 rpms or over 25 mph. It runs like it wants to run out of gas. Every once in a while on restart it will run fine until hit the accelerater. I have changed the glow plugs and the fuel filter. After i did this and got it started ran fine until I went to drive it. I got a 1/4 mile down the road and it started again. Does anyone have any suggestions?