KNOWLEDGE BASE: want to share your knowledge of this engine swap? Email me your tips and I'll post them here.

To mate up a 2002 system with the m3 manifold requires a Y shaped connector. This replaces the essential X pipe on a twin pipe system - all of which is explained in great detail here: e30m3 performance.

There's been a lot of discussion about what's the best size pipe for a single exhaust system, but the basic conclusions are that a 2.5 inch system is good for everything but the best flowing 2.5 litre which is better off with a 3 inch system.

The easiest solution is to buy an off the shelf turbo exhaust system and a Y connector from Dave Varco, but that's not to say it's the best for performance.

You can even fit a hybrid twin pipe system from the m3, although these were designed to run underneath the rear subframe and will compromise ground clearance.