My Alfa 166 has an intermittent problem. When I rev the engine then take my foot off the gas the engine revs drop very low after a second or so they return to normal tick over. Sometimes they drop so low that the engine cuts out. This problem will occur for a few days then go away for a bit. Any Ideas anyone? I seem to remember once when it went to an alfa serice agent they said it was the fuel control valve They changed it (£200 for a recon part) and it was ok for a year or two.