The Cat-back Exhaust System for the BMW 325/330 E46 is combination of bolt on pipes and slip fittings.
For US spec cars emissions are not affected as the catalytic converters are part of the exhaust manifolds. For Euro spec cars the catalytic converters will be eliminated.
XI (AWD) versions of the BMW E46 3 Series have a different shape upper pipe that connects to the exhaust manifolds. The Highline Tuning catback will not fit unless the first section of the midpipe is customized to match the factory shape.
Convertibles have brace at the rear of the vehicle with interferes with the Highline piping. The pipes will need to customized to be compatible with the bracing.