The flexi on the pre-cat downpipe on my CF3 Twinnie has seen better days and I have acquired a replacement with a new flexi welded in. So far I have managed to loosen off 3 out of the 4 nuts on the manifold to downpipe join. I can’t get to the last one (the back one nearest the engine) from above so will try again from underneath next time the car is jacked up. I’ve managed to free the long bolt that holds it to the engine. The downpipe to cat bolts are going to need an angle grinder though. Once they are all undone, does it just drop out or do I need to start removing other parts too? I’ve got a replacement gasket for the cat but do the fire rings need replacing too? Any advice much appreciated.