On the Superproduction motors, the spark plugs are on the intake side
instead of exhaust side on normal N9T motor.
There is also a racing head made by Danielson (official Peugeot ) but it's
not the biggest one. The spark plugs are on the exhaust side but at a
different place and they are really smaller than the normal ones.
Admission tubes are different a bit bigger also.
Comment:
One of these two must be what was on the 89 N9TEA that was listed at
the French Revolution.