Rusty_Rocket

12G202 is a good cylinder head, with those late collets I'd say it's most likely from a Clubman 1100. Have you checked between the rear wings and seat back for the foam strips? They were fitted there to every Mini saloon and further stop fumes entering the cabin. Most get binned when the cars are repaired as they get damp and encourage rust, but they're there for a reason. You can never totally seal the boot compartment from exhaust stink, too many small gaps and ill-fitting grommets!