I've had the BMS Stage 1 installed for a few weeks now. This tune has made the 28i so much more drivable. Driving in D is like what DS use to be (when you need it) and DS is on steroids now. The power delivery when going full throttle is not as smooth as my N54 335i was, but it feels almost as fast.
According to the folks on the F30 forum, BMW switched to the electronic wastegate on the N20 engines July 2012 (like the N26). BMWVin.com and RealOEM are generally pretty accurate and it seems that all US X1 28i have N20 and not N26. Sticker under the hood shows ULEV II. Either way, this greatly simplifies the BMS Stage 1 install/uninstall which doesn't require engine cover removal and takes less than 10 minutes.
Can't wait for Stage 2!
Originally Posted by Terry @ BMS
We've tuned around 250 N20/N26 motors now and the feedback has been phenomenal.
We've started working on a Stage2 upgrade box that plugs in to the Stage1 kit unlocking CAN features, more power, etc, so stay tuned for more HP.