Peugeot 306 fuel over burn

Hi, my peugeot 306 is over burning fuel. I took it into the garrage to have a few things checked out including inconsistent tone when running idle, and a slight resistance to pulling away, i also was getting a stron fuel smell when driving with my window down (deffinatly coming from my car). the diagnosis was that it was over burning fuel. the garrage tried to conect the car to a 'computer'. i was told by the garrage that the injection unit wasnt registering with their computer and that the solution was to replace the fuel injection unit (something i could eaisly pick up at a scrap dealer, and they would fit). does this all sound about right? mainly - does the car connect to the computer through the injection unit?

Many thanks