ok real easy
with pictures even
HEADER:
HEADERS:
the exhaust system uses one HEADER for each bank of cylinders
an inline 4 has ONE bank of cylinders.... thus uses ONE HEADER (most 4 cylinder cars)
an inline 5 has ONE bank of cylinders.... thus uses ONE HEADER (many audis)
an inline 6 has ONE bank of cylinders.... thus uses ONE HEADER (lots of BMWs, jeeps, lots of other cars)
a horozontally opposed 4 has TWO banks of cylinders... thus uses TWO HEADERS (subaru)
horozontally opposed 6 has TWO banks of cylinders... thus uses TWO HEADERS (subaru, porsche)
a V6 has TWO banks of cylinders... thus uses TWO HEADERS
a V8 has TWO banks of cylinders... thus uses TWO HEADERS
a V10 has TWO banks of cylinders... thus uses TWO HEADERS
a V12 has TWO banks of cylinders... thus uses TWO HEADERS
your honda engine is an inline 4, it has one bank of cylinders, it uses one header
so when talking about your exhaust the correct term is
HEADER,
not HEADERS
i really dont think it can be spelled out any clearer