I use the NON-Protusive NGK plug called the B6ES or equivelant Bosch spark plug, and i recommend them to anyone. They have the white part of the spark plug tip(the bit the centre electrode comes out of) 'inside' the thread part of the plug, thus reducing the amount of heat on the plug and reducing pre-ignition/detonation/pinging!
Its called the B6ES, the BP6ES spark plug is the protucive type(thats what the P stands for), so get the B6ES or equivelant.
Dont know about the exhaust gasket, but someone else will know....