My Mk3 2.0 16 has an odd problem. it starts and idles but as soon as you press the accelerator the engine floods and it cuts out. The only was to get it going is to press the accelerator really really slowly till the revs pick up. Then when its going it has no power at all. I have had a mechanic check everything and cant find any faults. Is the problem the ecu. How much would it cost to replace it?