the cat positioned lower is much better, it prevents there being an obstruction for the gases and in fact the turbine is cooled much better. The seletron emulator also manages to create fake signals for the 02 probes to avoid problems. the emulator is physically the same, you don't have to buy 2 but only one which works for both opf and o2 probesThe B9 didn’t have OPFs though, which is what the emulator is for. Or at least my 2017 didn’t.
The other issue is that all aftermarket sport cat downpipes I’ve seen (maybe there are some not like this) position the cat further downstream than the OEM placement so the post cat O2 sensor actually ends up pre-cat and the car throws a wobbly eventually as it thinks the cat isn’t working. I think that’s the bigger issue than the OPFs at the moment.
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