I have a T/A with all the mods listed below. Recently when I shut the car down exhaust comes out of the tailpipe for about 30 seconds. Could this be because I have an orp and it is getting colder outsider? Or is there something else that I should be concerned about?

 

It's just condensation in the exhaust evaporating, which is more noticeable when the air outside is cold. Nothing to worry about.