B58 Downpipe: A Complete Guide for BMW Performance Enthusiasts The BMW B58 engine is widely praised for its balance of power, reliability, and tuning potential. Found in popular models such as the BMW 340i, 440i, 540i, X3 M40i, and Toyota Supra, this turbocharged inline-six responds exceptionally well to performance upgrades. One of the most effective and popular modifications is the B58...