Finally did the climb, Strava puts the climb in Hors Category at ~55 km and altitute of 3275 m, which is our highest paved road.
My mistake was doing the reconnaissance climb in the M135i. I thought the climb would be easy because the M135i knock it out with its low down torque and mostly in 3rd gear. I was painfully wrong and was in the saddle for 4.5 hours. Another lesson learned, M135i has more horsepower than my legs
The point is I guess after 30000 km ownership still amazed by the performance and all the torque available low down and only likes the car more. I thought I'd need a second car when I got the M135i, it turns out I only need a bike rack. I would pick it again if I were to make the choice again. Okay maybe I'd look at the M235i only if it drifts better compare to a 1 series with LSD.