Gents, I am a newbie to this forum, so any help would be greatly appreciated. I have a early Euro spec F355 (2.7 engine). I also have a Tubi Pipe Only exhaust system (similar to a Spa Challenge system). I have been told that the cats have blown out, and are now hollow. My questions are: What would the effect of replacing the worn cats with test pipes be? Would I lose too much back pressure with this i.e. pipe only Tubi and worn cats/test pipes?? Should leave the cats as they are, or replace them? Thanks in advance, Roger.