New exhaust ! White smoke !please help !

Hello you guys ,sorry to disturb today I bought a Gruppe M Rep exhaust from a post on Craigslist . I installed the muffler and totally forgot to install the gasket ( dumb) that being said when I turn the car on Exhaust is super loud sounds very nice , but it was putting out a lot of white smoke smelled pretty bad , weather right now is about 20 degrees . Water drop were leaking from where the gasket goes ( will fix tomorrow ) car been off about 2 months now I had turn it on like 1weeks ago and was same as cold as today and there was no smoke i had the oem exhaust on though , we'll car was still cold had it on for about 10mins and turned it off cause the smell was very bad like Poisoning and lots of white smoke , once i turned off the car white smoke still kept coming out for like 5 mins
Could it be something wrong with my car or the exhaust ?
Has anyone ever had anything like this Happen To you ? Please help '!
Thank you


Car is a 2002 bmw e46 m3