Make sure it's got the large diameter baffles..............all the way through the silencer. Just look up the tail pipe to check that it's large bore all the way. Magnex were, but not all the other brands...........For that bhp, it MUST have a large diameter internal bore......Not just the tail pipe bit, otherwise you just strangle the engine. If you looked at the original Magnex that was on there, this was the LARGE bore exhaust.....4" all the way through to manifold. Alot of the other brands have a 4" tail pipe, and 4" bore exhaust pipe, but then it all goes pear shaped in the rear silencer/rear silence box when the diameter within the box is only 2"....... ! ! ! ! ! ! One of the reasons that she originally had a magnex system on there.