I don't think the standing pilot enters into the efficiency rating that much. The little you save in gas by going to an electronic ignition could cost you and your family their life. The new 90+ eff. furnaces vent with a blower to the outside through pvc. The old style are designed to vent out of a flue or b vent to the roof. Rule to remember is hot air rises and cold air falls. A constantly burning pilot from the furnace and gas hot water heater keeps hot air going up and keeps the flue pipe warm. When the furnace and hot water heater kick on, the combustion gas with CARBON MONOXIDE continue flowing up. Cold air outside flows down the vent and keeps the flue pipe cold if there is no constant heat. Until the flue warms up, a furnace being turned on in cold weather allows carbon monoxide to flow inside the house. Many people die in early fall and winter from this problem from a lack of upflow. Same theory applies to fireplaces and wood burning stoves which is why some fill up the room with smoke before the system starts to works. This is in addition to people dying from fires this time of year from creosote buildup in flue pipes that smoulders and catches house on fire. Just read where 6 out of 11 people in a family died last weekend for that reason. Moral of the story is to have a HVAC pro look at anything you are doing.