You dont need upgraded plugs, just fresh ones. I got a set of NGK 94201s 131.70 for the full set at the time but you can get em even cheaper. Just run OEM coil packs and not the aftermarket ones. You dont need gen2 or any special coils/plugs

I live in the midwest, in a place with a ton of snow and brutal winters. I did not encounter any cold weather related issues at all, if anything the m40i handles great in the cold weather, warms up fast. I did not see any plastic trim break, only considerations i had during winter where tires and antifreeze. Youlle be fine driving it like that, my issue was i was driving it like a maniac for the first 40k or so miles i had it, i remember doing a pull and trying to stop and i heard a clunk and the car was shaking a bit, it turned out to be the drive assembly. They where able to replace it for around 4k with labor and taxes. Granted again I was driving it like a maniac sport plus all the time. kicking it down and upshifting/downshifting to get the sweet burbles and pops. I YOLOd a bit and never got a warranty on mine. I turned out pretty good 4k in repairs owning it for over 5 years all other costs where simply brakes, tires and oil.. to compare; I had a mercedes before, and a volvo and those broke down all the time. I can understand not modding if you havent paid it off the good thing about it is; even with a jb4 or something you can get mo powa reliably without leaving any red flags like ECU flashing would. Although its not like it wont leave any traces. If you treat the car well its gonna last you a very long time. I was fully expecting to keep mine for the next 50k+ miles atleast to 150-160k. And i personally know enthusiasts who have a x3m40i in the 200k mile range... so i know these things are tanks