i got a 306 XD M Reg 1.6L quiet old petrol with 142000 miles, lol. i recently started getting a jerky feeling of lose of power as if the fuel isn’t reaching the engine, when i put some jet/engine cleaner through with the fuel it stops for a few weeks but then starts again, i have replaced the plugs and the fuel filters and still get it. the previous owner did say that the fuel lines had fuel in them just stagment for 12 months could this have something to do with it. Any ideas? :?