x5 50i Issues

[gutierrezb27]

I have 2016 X5 50i, and have some concerns I'm unsure about and was hoping to get some help. I'm stage 2 Bootmod,with downpipes.
i don't push the car, I pretty much drive like a grandpa to work and back.

- at cold starts, car seems to be rough idleing. You can feel the car vibrating/shaking. once in a while when i don't have time to warm up the car and i just drive. the car seems like its about to stall/hesitates to take off.

- ive noticed that after driving lets say on the highway or a long road, white smoke comes from the rear. even if the car is warm or cold it still happens. enough smoke for it to travel to the front and be visible to me and the passenger.

- I do oil changes every 4-6k miles, but in between oil changes i have to add 2-3 quarts of oil .

what is your opinion on what could be causing this? (spark plugs were replaced maybe 15k miles ago. (+ lower control arms, links,) )