Hello from the UK! Not that many 20G users over here so I though it'd be best to ask here!
I recently took the plundge and bought a Hahn Super 20G which I'm pretty happy with. I notice that the difference between the inlet on the exhaust and the outlet on the R manifold could do with some work to match them a bit but wanted some advice first...!
The T3 flange is square and the R manifold is round/oval. This will mean that there will be a flat wall that the exhaust gasses will hit on exiting the R manifold. Would it be worth matching these? The issue I see is that the turbo walls will be pretty thin once this has been done which may result in cracking of the housing. Has anyone done this? Is there a good reason why not if that haven't? I've got a ported head and I'm matching the inlet and exhaust manifolds.... it'd be a shame to then have this bloody great wall after all that work!
I know you can get the APT adapter, but this leaves me with the same problem, I am going to machine the R manifold flat, and can possibly make an adapter with the matching holes and then smooth them, but feel that this will need at least 15mm of plate that could compromise space in the bay (V70 P2 2002)
.... get some calipers... I know!