A couple of months ago i changed the lower intake gaskets in my 98 blazer lt and when i got it back together i noticed my gas mileage went from 21 mpg at 105kph to 17-18 and sometimes will hit 20 mpg if the wind is at my back.I marked the distrubutor when i took it out and put it back in making sure to line up my marks.Is it possible to be a couple degrees retarded or is it possible the there is a cylinder labouring because i overheated it trying to make it home when i blew the intake gaskets.