Hi i have a 04 wrx with a few mods on it but i have a smoke issuse i warm my scooby up before driving it and every now and thern (couple of weeks sometimes less) after i drive it a few mile when i come to a stop at idle thick white smoke comes plumming from the exhaust with a almost burning smell but soon as i pull away anf get to about 3000rpm it stops and dosnt come back till the next time it happens . Anyone have a clue what it could be ive had people say its coolant , head gasket , turbo to say a few please help