Simple question from a "newish" owner
 

I have owned my X for almost a month now, living in -20C weather, I wonder if you guys have the same situation with idling, just to confirm if mine is normal.

Cold start at 1100 rpm, slowly drops to ~650, pretty normal right?

but my warm start would stay on 1100 rpm forever. Is this normal too?

Also, warm car right after being driven, put it in "P", car idle at 1100 rpm too!

With resonator deleted and 1100rpm warm car idle, exhaust smoke is ridiculous, it almost like my car was on fire or something lol. Winter effect :D

Lots of (oil) smoke in very cold weather is probably a frozen CCV system. Don't continue driving like that - it is sucking oil into the intake and will get much worse very quickly. Of course white (water) smoke could be a cracked head or blown head gasket. None are happy news. Get it checked out ASAP. Preferably no more miles.

it's all white smoke, similar amount of smoke to my 335 with catless downpipe.

The larger amount of smoke came right after I cut the resonator out. It was minimal beforehand, I always thought large amount of smoke is a byproduct of no resonator/cat on car.

AFAIK, before I brought the car (it was owned by a BMW mech before). He did valve cover, CCV, and a bunch of different hoses.

As far as my visual inspection goes, I don't see any leakage in the engine bay. But I can't go further yet since my garage is taking forever for the contractors to build.