Hi guys, just a little update, I've popped the bonet on the beloved focus and give the cat a tap all the way round and can't hear anything other than a solid metal on metal thud. And just to confirm with myself more than anything I started the engine and revved the bollox off it using the accelerator cable in the engine compartment and couldn't hear anything out of the ordinary coming from the front end, I've just noticed from revving the engine by pumping the pedal there's no blowing sound when its stationary but there is what sounds like the exhaust kicking back, (that's the best way I can think of explaining it) I think I'm going to look back to the purchase of the back box just to confirm its the right part for my car cos I have slight suspicions its the wrong back box on there.