Why a Catless Downpipe N55 is the Best First Mod
If you're looking to wake up your BMW, installing a catless downpipe N55 setup is probably the single best bang-for-your-buck mod you can do. It's the gatekeeper to real power. The N55 engine is a fantastic piece of engineering—it's smooth, sounds great, and is generally more reliable than its twin-turbo predecessor, the N54. But from the factory, it's also a bit choked. BMW had to meet strict emissions standards, which meant stuffing a thick, restrictive honeycomb catalyst right behind the turbo. ...