And trying to start it cold on LPG if you don't have a gas system that injects a spray of petrol on startup - mine doesn't, and if I try to start it cold (even with new leads and cold plugs) the manifold simply fills with gas whilst it's trying to kick over and then ... BANG ... all that gas eventually ignites and as per yours, will more than likely blow the guts out of the airbox - you can fit a pressure release valve to it to assist this, but I just start on petrol and switch over to gas - no biggie.
More than likely those two prices above were actually correct - the box is sold by Nissan as two separate pieces, the top being about $180 and bottom being about $440 - $600 plus all up!! Not cheap and hence my hash job on a commodore VN airbox as a substitute ... Millweld release their all alloy airbox later this month, and whilst they will still be expensive, at least they'll never blow apart (and they'll look the sh!t too I reckon!! LOL) - I'll be getting one!!!