what size exhaust tube/elbow etc for my setup?

[s13eater]

i was going to mention that one, it was red, i had pics of it, it had a weired tubular manifold, someone told me it was 20ltr, i sold an et engine a couple of years ago craig, it was one of your scimmy crew, he fetched it for a friend, ithink he was from norfolk way.