I don't regard the alloy inlet as an upgrade - it's just different. The plastic inlet is lighter and doesn't need a support bracket. Some experts think the plastic inlet provides a bit more torque lower in the rev range. I'd take it off, check that its face is not distorted with a steel ruler then if it is straight, put in a new gasket (about £1).
Richard
1.8i Mk2 Solar Red, 16 inch square spoke wheels, MGFMania hood with zip-in glass rear window, DRLs, Kmaps ECU, Pipercross panel air filter, MGOC Supersports back box & some cockpit bling