[Darren69]

Whilst I've no experience of your situation exactly, I would say that its probably best to over size your exhaust. It certainly wouldn't be a bad idea to make it 50mm instead of 45mm but as I understand 45mm is the way to go for the 2v 900 at least with a spaghetti header. I'm currentlu running a 916 testabassa S4 motor stock with 45 headers and mid section into hi level 50mm link pipes with probably about a 10% increase in mid and top end. I think stock is 40mm all through. So restricted. But with a 2v you can teally feel it (head flow restriction).