Probably like you say for performance by the uneducated lol, as for the pass my 1.3 is supposed to have 2 cats, the second of which was removed and the o2 senor Had packed up I replaced it with a bolt and it still passed emissions, mot guy stood scratching his head when he looked under the bonnet to see a 4 inch long bolt( only one the right size I had) stuck out the o2 port, one of those o2 extender plugs worked to get the light out on my mx5 but they’re trial by error may work may not