[abbike18]

Hi All-
I put the Stage 1 91 octane BM# tune on my '19 X3 M40i a few days ago. Wanted to give my thoughts below to help someone who is thinking about this.

First, numbers. I'm at about 5200' elevation (so tend to be slower) and do my 0-60 runs in the exact same spot. I use the Bimmergeeks ProTool performance timer, which simply reads the speeds off the unaltered digital speedometer. Car has the 20" staggered setup (273 in the rear) with the M Sport rear diff.

Stock - 4.75s (dry roads, Pirelli P zeros, mid 50s F)
xHP Stage 2 - 4.6s (dry roads, Pirelli Scorpion Winters, 28 deg F)
xHP Stage 2 and BM3 stage 1 91 - 4.02s (semi wet roads, Pirelli Scorpion Winters, 27 deg F)

On impressions:
Comfort - It is worth noting here that you get a lot more boost build at lower RPMs. This is good for speed, but keep in mind that it gives that turbo lag feeling. I have a feeling that BMW stock tune just didn't let the turbo spool here, so it feels less laggy but is also slower.
Sport/Sport+ - Obviously, its way faster. Feels like a real sports car. Chassis can handle the power as well. My only complaint is that the throttle mapping is extremely non-linear. You really go through a lot of the throttle in the first title bit of the pedal.

Otherwise though, it takes the M40i from a fast SUV in to a total beast. I really can't imagine what Stage 2/2+ do. I imagine that a downpipe would really help the turbo lag feeling at lower RPM.