My engine has been running extremely rich since I rebuild the top half about a month ago. Twice in the last week it has flooded after a few minutes of driving. It's a '91 TBI 350 and the only thing that has been changed on it is a colder thermostat. I going to put the stock thermostat back in it today, but what else could cause my engine to run that rich? I don't think that a thermostat alone would make it run so rich that it stalls out? The wheather is starting to get cold around here, that is why it started acting up this week. What can I do to lean the engine out before winter hits? Any help would be appreciated. Thanks.