I have some oil leaks on my Duratec (roller barrel TBs) which I believe may be down to a breathing issue. Should I leave the PCV valve in place or discard it? I am about to investigate further this pm but wanted opinions too.

Remove the PVC valve when using ITBs

see this thread http://www.locostbuilders.co.uk/forum/9/viewthread.php?tid=146519

hope that helps

That's great, thanks for the link much appreciated.