The N54 is the best bang-for-buck inline-6 BMW ever made — and it's not even close. A stock 335i with the 6-speed manual already puts down numbers that embarrass cars costing twice as much. But with the right build order, you can push past 400whp on stock internals without turning your daily into a grenade. The key is doing it in the right sequence. Here's the roadmap: → Why the N54 responds to mods better than almost any modern turbo engine → The maintenance items you HAVE to knock out before you touch a tune → How to hit 400+ whp with full bolt-ons and keep your wastegates alive → Wheel and tire specs that actually clear Brembo brakes and look right on E90 fenders → A realistic budget breakdown so you're not guessing Too many people flash a JB4 on day one with original charge pipe and index 1 injectors, then wonder why they're chasing boost leaks in a parking lot. Don't be that guy. Fix the known failure points first — OFHG, water pump, charge pipe, injectors — then build power on...