I have a 2015 X5 s35i that recently started acting up shortly after startup. The pattern is the same: I jump in the car and drive to the gym (1 mile away). On the last stretch of the drive I accelerate to 45 on a main road. When I slow down to turn, the engine starts to stutter and the accelerator goes soft for about 3 secs (no power while the engine is coughing). In one instance, black smoke shot out of the exhaust although I haven’t had that happen the last few times. RPMs in idle stay slightly elevated (around 1k) and the car feels a little rough while idling (although I’ve always felt these cars tend to idle a little rough). No error codes and my mechanic hasn’t been able to replicate the issue. Any ideas on what might be going on? The car only has 76k miles on it (I work from home and drive my Z3 during the cooler months in AZ) and I’d love to keep it for my son who starts driving in 2.5 years but this issue is frustrating. Any suggestions are greatly appreciated!

x5 #s35