Hey guys I've searched all over the site and online but seem to be getting all kinds of mixed opinions. I have a 96npi motor basically stock. I have coolant in all four spark plug holes on the drivers side, nothing on the passenger side. No milky residue in the oil, no bubbles coming from the coolant reservoir while running, and minimal white smoke out of the tail pipes (it is cold outside, this may be why?) not running hot, and I recently replaced the thermostat. It doesn't look like the thermostat is leaking, or anything else at the top of the engine really. Could this more likely be a head gasket, intake, intake gasket, or anything else? Thanks for any help!