Thanks Bab, that's what I wanted to hear, sizes too. I'm ok to fab the down pipes. Mine has a cat in the down pipe and another in the primary down pipe- do I need to run both to keep the ECU happy? I was thinking just one high flow in the centre pipe.
Also since Ive had it the O2 sensor for the centre cat has been unplugged. It has one plugged in in the in the primary down pipe and another somewhere maybe the primary up pipe. I cant find a corresponding plug for that rear O2 sensor. It runs fine but does it need it? I have seen cars before where they place an O2 sensor before and after a cat foe emissions or something that does nothing for the running of the car- is this that sort of thing?
Another thing I noticed when changing my primary turbo is that the up pipe diameter is much larger than the inlet of the turbo and the junction is all right angles. I don't know why they would do this but it looks like a major flow restriction- can the turbo inlet be ported?
Cheers