The pre-cat has been known to fail and either collapse on itself or crumble and
clog the main catalytic convertor further down the exhaust system. As
a purely preventative procedure, we inspect ALL pre-cats to make sure they
are intact. If the pre-cat is failing, you can punch out the rest of the
pieces with a piece of pipe or equivalent. If you find the pre-cat in
pieces, we highly recommend to inspect the main cat for clogging! The pre-cat
was designed by Mazda to clean up emission, especially at cold-start. J-spec
FC's do not come with pre-cats, and in fact come with a downpipe - stock.
If your FC is down on power, and water temps are abnormally high, check the cats
to see if they are failing.
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