In April 2003 i bought the same car as yours. For one year i had the same problem as you, even worse. Mine started to decelerate even in highway, suddenly for 2-3 minutes and suddenly again was coming to normal condition. I was very very sad and i couldn´t find the reason for this.
One day ()i decided to put one of those diesel power booster chips just to increase the power, i didh´n imagine that this could solve my problem. And yes as a miracle this problem disapear. since 2004. I still own this car and i have never face any other problem. I don know if it is just i coincidence or not. i´m just telling you my experience. it cost me 500 euros that chip. I can connect and disconnect it (bypassing it) and it doesn´t make any difference. No problem at all. And this chip does boost the power and you feel it. it was worth it either way.
regards from Cyprus
? Hello,