I have a 2003 mustang gt auto with a bad trans im getting it replaced but it has borla attack exhaust with no cats on it and no muffler and ive noticed that alotnof white smoke comes out of it only at start up and if you rev it at idle is that normal because ive started to red on it and some people says its normal and some says it a head gasket probably ive checked the oil cap alot there is no weird gunk on it and some also say its because i need a new trans my auto neutrals out shifting at 3-4 please help