The first-ever M versions of the X3 and X4 broke cover somewhat unexpectedly in February 2019, joining the larger X5 M and X6 Mto complete BMW’s four-vehicle lineup of beefed-up SUVs. And, while the X3 M, the first of its kind in 16 years, is big news, there’s even bigger news under its hood, where BMW dropped a brand-new high-performance engine. It’s called the S58 and replaces the already iconic S55.