My local mechanic just changed my timing belt, water pump, battery, hydraulic tensioner, tensioner pulley and idler pulley. Now it start instantly, rev's nicely above 1750 rpm. It pulls really nicely when doing a test drive. When Below that it's just a little rough and at about 1200-1500 rpm it seems to miss just a little. He said it takes a little while to re-learn everything after the battery was disconnected for several hours. should I be worried?