volvo s60 d5 se

Hi im having trouble and need advise
My volvo s60 d5 se ran out of deisle once got it going again but since then it keeps hessitating needles going eratic message saying engine service urgent then dissapears then its ok and it does this every time i go further than 20 miles or on the odd occasion small journeys i have tried a new fuel filter and diesle injector cleaner my next move is a cheater injector unit allowing more bhp and bypassing the original sencor to see if its the sensor any other suggestions oh its a 2001